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Cosmetics Ingredients
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Cosmetics Ingredients
Preservatives

Cosmetics Preservation – An Ultimate Guide to Select the Right Preservative

Cosmetic products require preservation against microbial contamination to guarantee consumer’s safety and to increase their shelf-life. Preservatives are essential ingredients that help preserve the integrity and stability of cosmetic products that can be damaged by microorganisms. While there is a wide variety of preservatives available, either synthetic or natural, choosing the right one for your cosmetic formulation could be a task.

Explore what are the different types of preservatives, their features and get tips for making the right selection for your formulation.

We would like to acknowledge Belinda Carli, Dr. Barbara Olioso for providing technical information needed to develop this guide.

Overview

Why is preservation important?

Why is preservation important?

Several products in the market contain ingredients which make cosmetic systems very difficult to preserve. For example, products often contain significant amounts of water and other organic or inorganic ingredients that may be susceptible to contamination by microorganisms like bacteria, fungi, and molds.

Most cosmetic care products must be protected against microbial growth – for both consumer protection and formulation stability reasons. Growth of microorganisms might result in degradation of ingredients and consequently in deterioration of physical and chemical stability.

In order to prevent such happenings, formulators include preservatives in their formulations. Depending on the type of preservative selected, they can:

  • Kill or inhibit the growth of micro-organisms, and
  • Protect a formula from microbial contamination

Moreover, microbial growth can also be prevented by using sterile or aseptic production and filling into packaging material, preventing microbial contamination during storage and usage. Also, while applying a cosmetic for personal care use it should be assured that its free from any contamination. The product must be preserved adequately to kill the microorganisms that are introduced by the consumers themselves.

 One also must be careful with over-preserving a product as too much preservative in a product is not good either

As formulations become more complex, proper selection and addition of preservatives becomes a critical formulation issue for the following reasons:

  • Preservatives can interact with other components of the formulation, e.g., with emulsifiers, leading to change of viscosity or phase separation.
  • Depending on the physicochemical characteristics, preservatives are distributed between the different phases which might result in too-low effective concentration in the aqueous phase.
  • Adsorption of the preservatives to polymers in the formulation and/or packaging material; complexation or micellization might also result in too-low antimicrobial activity.

In conclusion, preservation can be a great formulation challenge to achieve sufficient microbial protection. To protect the formulation sufficiently, a properly designed preservative system is required that must be tested in the formulation regarding efficacy and safety.

In this guide, you will learn about the different preservation options are available today, different chemistries & criteria to select the right preservation system for your formulation.


Cosmetics Preservatives – Types of Chemistries Available

Cosmetics Preservatives – Types of Chemistries Available

  • Preservatives, sometimes also referred as "antimicrobial agents", are cosmetics ingredients added to provide bactericidal or bacteriostatic activity during production, storage and usage of any product. Their main function is to protect and maintain the integrity of product - efficacy, fragrance, appearance, and stability - during its life by providing a preservative efficacy against microbial contamination.

Different preservatives have different ways of working based on their chemistry. Tables below lists some common types of preservatives used in cosmetic formulations and their key features, activity spectrum and functioning range as well as suggested use levels.

Preservative Type Features Examples
Organic acids
  • Effective with fungi but offer least protection against bacteria
  • Effective only in acidic conditions (pH 5.0)
  • Need an aqueous base, in order to be used
  • Considered natural alternatives while developed synthetically
  • Need to be combined with other preservatives to provide broad-spectrum action
Alcohols and Phenols
  • Effective against a wide range of microbes
  • Combination of phenethyl alcohol with caprylyl glycol shows a synergistic antimicrobial effect
Parabens
  • Mostly used preservatives with cosmetics (both rinse-off and leave-on)
  • Cost-effective
  • Rendered inactive in combination with polysorbate emulsifiers
  • Good protection against fungal growth and gram-positive bacteria
  • Can be used at levels ranging from 0.01 to 0.3%
Urea Compounds / Formaldehyde releasing preservatives
  • Effective in fighting bacteria but weak fungal efficacy
  • Low levels required for use as these release formaldehyde needed for preservation
  • Can cause skin irritation / allergic reactions
  • Used in skin care and toiletries
Isothiazolinones
  • Activity is related with the thiol and amine groups of their structures
  • Often masked under the chemical names of their mixtures
  • Can cause skin irritation / allergic reactions
  • Methylisothiazolinone
  • Benzisothiazolinone
  • Methylchloroisothiazolinone
Quaternary Ammonium Compounds (QAC)
  • Antimicrobial activity of the QACs is a function of the length of the N-alkyl chain
  • Optimum activity against Gram-positive bacteria and yeast is obtained with chain lengths of 12 to 14 alkyls
Alkyl (C12-22) trimethyl ammonium bromide and chloride
  • Behentrimonium Chloride
  • Cetrimonium Bromide & Cetrimonium Chloride
  • Laurtrimonium Bromide & Laurtrimonium Chloride
  • Steartrimonium Bromide & Steartrimonium Chloride
  • Benzalkonium Chloride
Material Selector - Find Suitable Preservative Grade for Your Cosmetic Formulation »


Preservative name Activity spectrum Compatible with Inactivated by Optimum pH
Parabens: esters of benzoic acid Fungi, Gram + Cationic Anionic, Non-ionic, Proteins < 7
Imidazolydinil urea Broad, Weak Anionic, Non-ionic   4 - 9
Diazolydinil urea Against fungi Cationic, Proteins    
Isothiazolones Broad Anionic, Non-ionic, Cationic Bleach, High pH 4 - 8
Formaldehyde Broad Anionic, Non-ionic T° > 60°C 4 - 9
DMDM hydantoin   Cationic    
Benzalkonium Cl Gram +, Gram -, Weak against molds Non-ionic, Cationic  Anionic, Proteins, Soaps 4 - 9
2-bromo-2-nitropropanel, 3-diol Broad Anionic, Non-ionic, Cationic  Heat, High pH, Cysteine, Aluminum < 6
Abbreviation: DMDM, dimethylodimethylhydantoin
Most Commonly Used Preservatives


INCI name Maximum concentration & Product Type
Benzoic acid/Sodium benzoate
  • 2.5% (as acid) - Leave-on products other than oral product
  • 0.5% (as acid) - Leave-on products
Salts of benzoic acid and esters of benzoic acid
  • 0.5% (as acid)
Benzyl alcohol
  • 1%
Sorbic acid and esters of Sorbic acid
  • 0.6% (as acid)
Triclosan
  • 0.2% - Mouthwashes
  • 0.3% - Toothpastes, Hand soaps, Body soaps/ Shower gels, Deodorants (other than spray products), Face powders, Foundation, Nail products for cleaning the fingernails and toenails before the application of artificial nail systems
Phenoxyethanol
  • 1%
Phenoxyisopropanol
  • 1% - Rinse-off products
Parabens - 4-Hydroxybenzoic acid and its Methyl- and Ethyl- esters, and their salts
  • 0.4% (as acid), single ester
  • 0.8% (as acid), mixtures of esters
Diazolidinyl urea*
  • 0.5%
Imidazolidinyl urea*
  • 0.6%
DMDM hydantoin*
  • 0.6%
Bronopol*
  • 1%
*When used as preservatives in cosmetic products, the total amount of released free formaldehyde should not exceed 1000 ppm
Methylisothiazolinone
  • 0.0015% - Rinse-off products
Methylchloroisothiazolinone (and) Methylisothiazolinone (Mixture 3:1)
  • 0.0015% - Rinse-off products
Alkyl (C12-22) trimethyl ammonium bromide and chloride
  • 0.1%
Benzalkonium chloride, bromide and saccharinate
  • 0.1% (as benzalkonium chloride) - Avoid contact with eyes

The chemistries discussed above can be used in synergy to improve the activity spectrum. For example, the parabens can be used with the Imidazolidinyl urea, the formaldehyde can be used with the EDTA, and so on. Most of the preservative manufacturers have developed their own synergistic mixtures of chemicals; this allows them to use lower levels of each chemical and thus decrease the toxicity potential with increased preservative efficacy.

**IMPORTANT: Do not confuse Antioxidants for preservation. Protection against oxidation may also be a formulation issue although not so relevant as antimicrobial efficacy. The primary function of antioxidants is to delay the auto-oxidation of unsaturated oils that could influence the color and the odor of the product.

Careful preservative selection is essential to make sure the preservative or preservative blend provides broad-spectrum protection and is suited to the product being created. Additionally, these ingredients must be compatible with the other ingredients of the formula as well provided targeted efficacy & stability for an extended period of time.

Ensure your new or revised formula meets the chemical, physical and microbiological quality standards »

While speaking of it looks easy but formulating with preservatives can sometimes be very difficult.

As a formulator, you must do ample research to find the right combination of preservatives to kill any contaminants that may be present or find their way into cosmetic products. It is also advised to consult appropriate preservative manufacturers to select the optimal preservative system for the emulsion.


Criteria to Select the Right Preservative

Criteria to Select the Right Preservative

The selection of a preservative for a formulation is undoubtedly one of the most important, yet most controversial, aspects. With so much of choices in preservatives available, and so much misinformation on the internet, how can you make the Perfect Preservative Selection?

In general, liquid- and emulsion-based cosmetic products are the most susceptible to the development of micro-organisms. Powdered products, such as talc, are also susceptible to contamination and need to be preserved.

There is no single preservative that will suit all formulation types and company/product philosophies or product types. Technically, any preservative that is used within limits as specified by regulators in a particular region, and was suited to the product type and end consumer, is suitable for selection.

Despite popular (yet misinformed) reports on the internet, preservatives when used within limits specified by the regulators are considered ‘safe’ and suitable for use. So just how you can make the best, if not the ‘Perfect’, preservative selection?

There are some key elements that need to be considered, and they are discussed below.

Company/ Product Philosophy


The first selection step you need to make is based on the company and/or product philosophies, particularly if there are claims being made about ‘natural’, or ‘avoiding’ the use of certain ingredients and/or if Organic certification (or other certification, for that matter), is required.

  • If a company specifically requests the ‘avoidance’ of certain materials, then preservatives containing those materials must be specifically avoided.
  • If a company is after certification, then only preservatives that comply with the Certifier’s requirements may be selected.

As a first step in the preservative selection, company/product philosophy and the specific use or avoidance of certain ingredients obviously narrows the choice of preservatives that can be used depending on the selection criteria specified.

Steps you need to make is based on the company/product philosophies
Steps you need to make is based on the company/product philosophies

Also, part of the company/product philosophy considerations is:

  • On whom will be the finished product used? For example, babies vs. children vs. adults.
  • What part of the body will it be used on? For example, mucous membranes vs. around the eyes vs. external skin of the legs.
  • Will the product be washed off or left on; and how often will it be applied? For example, wash off products with relatively short contact time vs. regular use products that are to be left on the skin.
  • Does the preservative carry an aroma that may (or may not) be suited to your target market and product requirements?


Regulatory Considerations



For use in a personal care product, preservatives must be:

  • Permitted in the countries in which the product will be sold, and
  • Used within any limits or conditions of use specified.

For example, most preservatives have very specific ‘limits’ on addition, and can only be used within the limits specified.

Other preservatives may have very specific conditions of use, for example, in wash-off products only, or not on mucous membranes. In such cases, conditions of use must be adhered to, to ensure regulatory compliance of the finished product.

Cosmetics RegulationsLimits and conditions of use imposed by regulators have generally been set based on evaluations of safety. So, using preservatives in compliance with the regulations is not only a legal requirement but also an important safety consideration to ensure ‘safety when used as directed’ of a finished product.

Must Read: Cosmetic Regulations Round-Up – Impact of Ingredients & Claims »


Product Form


The form of the product will be the next biggest selection criteria, which can impact on preservative selection based on:

  • Finished product transparency required (or in the case of emulsions, this may not be important at all!)
  • Dispersibility/solubility of the preservative: ensuring a preservative can be easily and homogeneously distributed is crucial to ensure a product is adequately preserved in all areas of a large vat!
  • Chemical nature of the product: some preservatives are particularly not suited to charged (anionic or cationic) environments while others may work better in these mediums
  • Free water content and Microbial Risk Classification (MRC) of materials used in the formulation: materials with higher risk ingredients will need stronger acting preservatives; this does not mean one should ‘over-preserve’ a product, but that careful selection needs to be made to ensure broad-spectrum coverage and synergy of blends used to ensure adequate microbial protection of the finished product


Compatibility and Stability


To choose an active antimicrobial molecule as preservative is not so easy. A good preservative must have a good O/W partition coefficient, since this will allow enhancing its activity in the aqueous phase of the formula. It must not be inactivated by external factors such as the pH and the manufacturing process. The inactivation of the micro-organisms by the preservative should be sufficiently fast to prevent any adaptation or resistance to the preservative system.

Several factors may influence the stability of preservatives such as solubility and partition in oil/water (O/W) or water/oil (W/O) emulsions, formulation pH, and temperature during use, and the volatility of the preservative. In addition to it, a suitable preservative must be compatible with other components of a cosmetic formulation such as surfactants, solvents, pigments, fragrances, and other ingredients.

Testing Stability of Your Cosmetic Formulation


So, the ideal preservative system must be selected for each formula, taking into account the possible inactivating ingredients or the potentiation capacity of other ingredients.

Other factors, such as the packaging also have to be considered which could affect the preservative activity, the adsorption rate on some components of the formula, the solubility of the preservative molecule and its volatility. Physical compatibility is also important. The addition of a preservative can influences the appearance of the cosmetic product and, for this reason, must be tasteless, odorless, and colorless.

pH


Finally, and just as importantly, the pH of the finished product is essential to be considered. This includes not just the pH of the finished product when it is manufactured, but must also allow for pH drift over the shelf life of the product. The pH of a product containing water will move over its shelf life. It is quite typical for the pH of a finished product to move +/- 10% over its shelf life; sometimes this drift can be up to +/- 20%!
Select your Preservative with pH Drift of +/-10%
Selecting a preservative with a limited pH range of compatibility could leave your product un-preserved in case large pH drift occurs. So, when selecting your preservative, make sure you consider a potential pH drift of at least +/-10%, if not a little more, to ensure adequate efficacy of the preservative over the shelf life of the product.

Important to Note

  • In O/W emulsions, lipophilic preservatives, such as parabens, may be distributed in the lipid phase and the product actually becomes unpreserved.
  • Parabens are, for example, are ineffective in alkaline formulations due to their dissociation at this pH. The antimicrobial activity of parabens may be altered, in particular, by non-ionic surfactants.
  • Bronopol also undergoes slow decomposition at high pH.
  • Formaldehyde donors may undergo slow decomposition in aqueous media. Formaldehyde is also influenced by many types of organic compounds, such as surfactants and nonionic proteins.
  • The action of salts or alcohols depends on the osmotic effect.
  • The presence of high concentrations of solid minerals (carbonates and silicates, among others) or organic solids (cellulose and starch) causes absorption of preservatives.
  • Certain ingredients can produce a synergistic effect with some preservatives. E.g., EDTA is known for its synergy with several chemical preservatives.

Self-preserving Cosmetics – What’s the Catch?

Self-preserving Cosmetics – What’s the Catch?

Another way to preserve a product is to build a ‘‘self-preserved’’ formula by using raw materials that are not supporting germ growing and optimizing their relative content.

In self-preserving preparations, traditional preservatives have been replaced by other cosmetic ingredients that exert antimicrobial activity. Substances which have been used in self-preserving preparations are caprylyl alcohol, fatty acids, and their monoesters such as glyceryl monoester of caprylic, capric, and lauric acid, ethylhexylglycerin, chelating agents such as citric acid, lactic acid, and ethylenediaminetetraacetic acid, phenolic antioxidants, plant extracts, essential oils, and fragrance ingredients

  • The use of essential oils like tea tree oil or geraniol or eucalyptol or humectants such as glycerin or sorbitol at a sufficient level increases the formula resistance.
  • Other ingredients, such as alcohols, cationic detergents, fragrance components, and lipophilic acids (lauric and myristic acids) used as emulsifiers, which have intrinsically antibacterial properties, can contribute to the self-preservation of a cosmetic.

Some physical factors, such as the pH and the formula water activity, can also contribute to build a self-preserved product. Micro-organisms are essentially living at pH of around 5 to 8, and any pH outside this range induces difficult life conditions for bacteria. The water activity or availability is an important factor as the water is a necessary ingredient for bacterial growth.

Download Brochure: E-Leen® 8, P8, GC8: Eco-friendly solutions for self preserving natural cosmetics


Self-preserving Cosmetics – What’s the Catch?

Self-preserving Cosmetics – What’s the Catch?

Another way to preserve a product is to build a ‘‘self-preserved’’ formula by using raw materials that are not supporting germ growing and optimizing their relative content.

In self-preserving preparations, traditional preservatives have been replaced by other cosmetic ingredients that exert antimicrobial activity. Substances which have been used in self-preserving preparations are caprylyl alcohol, fatty acids, and their monoesters such as glyceryl monoester of caprylic, capric, and lauric acid, ethylhexylglycerin, chelating agents such as citric acid, lactic acid, and ethylenediaminetetraacetic acid, phenolic antioxidants, plant extracts, essential oils, and fragrance ingredients

  • The use of essential oils like tea tree oil or geraniol or eucalyptol or humectants such as glycerin or sorbitol at a sufficient level increases the formula resistance.
  • Other ingredients, such as alcohols, cationic detergents, fragrance components, and lipophilic acids (lauric and myristic acids) used as emulsifiers, which have intrinsically antibacterial properties, can contribute to the self-preservation of a cosmetic.

Some physical factors, such as the pH and the formula water activity, can also contribute to build a self-preserved product. Micro-organisms are essentially living at pH of around 5 to 8, and any pH outside this range induces difficult life conditions for bacteria. The water activity or availability is an important factor as the water is a necessary ingredient for bacterial growth.

Download Brochure: E-Leen® 8, P8, GC8: Eco-friendly solutions for self preserving natural cosmetics


Green Alternatives for Cosmetic Preservation

Green Alternatives for Cosmetic Preservation

It should be noted that apart from being compatible and efficient; the antimicrobial system needs to be:

  • Safe to use,
  • Compliant with the regulatory authorities, and
  • Environmentally sustainable.

Features of Antimicrobial System
Features of Antimicrobial System

However, the major dilemma that cosmetic formulators face today is whether to use:

  • Conventional preservatives: That consumers do not like and do not trust, and that might be banned sooner or later in any case, or
  • Multi-functional ingredients: That have additional antimicrobial properties, in line with a product’s green positioning and message for the consumer

The second option is certainly more complicated. Thus, many formulators probably wonder why they should bother making their work more complicated than it already is.

Gaining Consumer's Trust is Not that Easy


Consumers are concerned about their own health as well as the planet. They are also becoming increasingly informed and knowledgeable with the ingredients found on the label. Despite their lack of technical knowledge, they know where to find detailed information. They use platforms such as the EWG site to decide if they can trust a certain ingredient - and therefore product that contains it - or not. The claim that a product complies with the current legislation is not enough for them.

Shrinking List of Available Approved Preservatives


It is really unfortunate that, after the parabens restriction, the exposure to some preservatives (such as MI and MIT) went sky high. This caused a lot of dermal outbreaks and subsequent mistrust in the industry. This is causing instability problems in some formulations and potentially another dermal outbreak.

Another source of current pressure is the shrinking list of available approved preservatives. In the last few years, there has been rising restriction of certain preservatives like Quaternium-15, Chloroacetamide, Formaldehyde and Paraformaldehyde.

The restrictions decrease the range of preservatives left to use. As consumers enjoy using cosmetics as part of their wellbeing routine, the amount of cosmetics exposure they endure keeps on increasing, making safety assessment more complicated and less predictable. Given the longer and longer yards of red tape, it is very unlikely that raw materials manufacturers will invest in the registration process of new preservatives, making future cosmetic preservation a real challenge.

Switch to natural preservative alternatives to meet green cosmetics labels »


Your Quest to Safe & Natural Cosmetic Preservation Ends Here

Your Quest to Safe & Natural Cosmetic Preservation Ends Here

Safe & Natural Cosmetic Preservation Synthetic preservatives are being scrutinized more every day as health hazards, irritants and just plain not good. Some are linked to various types of cancer while others are claimed to have some other potentially harmful side effects although the testing has not really shown that all synthetic preservatives fall into this category.

Yet the industry, in order to keep with the growing need for safer products is slowly trying to eliminate them from formulations. This will be a very slow process as the functionality of natural preservatives is obviously not the same as for their synthetic counterparts.

In searching for additional natural preservatives, suppliers are presenting more and more alternatives to the cosmetics formulator and several unconventional ingredients are being used. These new ingredients, although not truly considered preservatives by definition, have been tested to see if just by their chemical nature, they can function as microbe-killing ingredients. Many of them work in synergy with other ingredients while others strengthen the effect of some ingredients' already known natural bacteriostatic properties.

In searching for additional natural preservatives, we can see that it is an industry-wide process with many suppliers making these offerings. 


Much of the work involves simple (and sometimes complex) biochemistry and the understanding of the physical properties and functionality of the cells themselves. If an ingredient can alter the function of the cell membrane in a specific application, then it could be that the ingredient, when strategically placed in a formulation, might act with preservative-type properties.

Learn about some of the natural preservation options available today.

Essential Oils


They have antimicrobial activity and have been proposed as natural preservatives. The antimicrobial effect of essential oil depends on content, concentration and interactions between the main active compounds. Some of the common oils used include tea tree (Melaleuca alternifolia), thyme (Thymus vulgaris), lemon grass (Cymbopogon citratus), oregano (Origanum vulgare), rosemary (Rosmarinus officinalis), calamint (Calamintha officinalis) or lavender (Lavendula officinalis) and many others. View Several Essential Oil Grades with Antimicrobial Activity »

Mold, yeast, and bacteria are very abundant in the soil, breaking down dead plant tissue and supplying nourishment to the healthy ones. The ingredients obtained from plants have been determined to contain natural antibacterial properties.

So, we ask the question, can we use these same natural ingredients in cosmetic to serve this same function?
Is it legal if we do so?

The answer is yes to both questions.

The use of plants and plant extracts as natural preservatives is now very commonplace. Who would have ever thought that ingredients such as Aloe Vera, Grapefruit Seed Extract or Sorbitol would have these benefits? And there is no legislation that prohibits their use as anti-microbial agents.

Natural Preservatives Based on Alcohols


Rationally, they are synthetic molecules and some of them does or does not occur in nature. For example, propylene glycol does not exist in nature and naturally, it is derived from the fermentation of corn. It is used as a humectant but can also act as a preservative because of the -OH (hydroxyl) groups attached to the molecule making it function like an alcohol which by nature can act as anti-microbials.

Recommended products for preservation of natural cosmetics are discussed below.

  1. A-Leen® 5 (formerly called Pentiol Green +) by Minasolve
    • INCI: Pentylene Glycol; Use level: 0.5 >5.0%
    • Renewable alternative to petro-sourced Pentylene Glycol
    • 100% Derived-natural, Ecocert COSMOS approved

  2. E-Leen® 8 by Minasolve
    • INCI: Caprylyl Glycol (and) Glycerin (and) Aqua
    • Derived from sustainably sourced coconut and palm kernel oils
    • 100% vegetal, ECOCERT verified and COSMOS & NATRUE approved

  3. Zemea® Propanediol by Tate and Lyle
    • INCI: Propanediol
    • Preservative-boosting humectant which can replace petroleum-based glycols such as propylene glycol, butylene glycol and glycerin
    • Certified by NPS and considered organic ingredient under the definitions of ISO 16128-1

  4. Hydrolite® 5 green by Symrise
    • INCI: Pentylene Glycol
    • A by-product coming from sugar cane
    • 100% bio-based carbon, COSMOS approved


Organic Acids and Their Salt Derivatives


Moving further into the world of organic chemistry and functional molecules, we come across a wide variety of materials.

Propionic acid occurs naturally in grains, apples, strawberries and cheese salts of propionic acid sodium propionate, calcium propionate potassium propionate and myristyl propionate.

Benzoates are derivatives of benzoic acid and are natural preservatives which are tasteless and odorless, and which are used to extend the shelf life. Benzoic acid work best at a low (acidic) pH. It can be toxic in large amounts and can irritate the skin at high levels, which is true for any preservative. Don't forget, they are designed to kill microorganisms, so large amounts can be hazardous. Some common benzoate derivatives are calcium benzoate, potassium benzoate, sodium benzoate and benzyl benzoate.

Ascorbic acid is a vitamin which can be used as the organic salt of the acid. It exists in many plants but especially in citrus fruits. It can be used in both foods and cosmetics. It has excellent antioxidant qualities. Ascorbyl palmitate is a fat-soluble form of vitamin C that functions well in cosmetic oils and emulsions. Ascorbic Acid works better in water soluble products. Ascorbic acid is a non-toxic substance and does not irritate the skin. A large amount is needed for it to be effective in cosmetics. It works well when combined with Vitamin A (retinyl palmitate) and Vitamin E (tocopherols) to give broad-spectrum antioxidant activity. It protects against bacteria and some viral diseases. A cosmetic product that contains both ascorbic acid and ascorbyl palmitate is protected against microorganisms in both the oil and water phases of the product. Common forms are ascorbic acid, ascorbyl palmitate and magnesium and sodium ascorbyl phosphates.

Sorbic Acid and its salts of sodium sorbate, potassium sorbate and calcium sorbate. Also in common use is Acetic acid and its salts dehydroacetic acid and sodium dehydroacetate.  View Sorbic Acid and Its Derivatives Here »

Other ingredients act as preservatives by enhancing other natural preservative systems they are used in tandem with them to provide optimum antimicrobial effects with the elimination of conventional synthetic preservative systems. Such ingredients are gluconic acid, glucono delta lactone, glycereth-2 cocoate, C4-18 perfluroalkylethyl thiohydroxypropyltrimonium chloride, polyaminopropyl biguanide, caprylyl glycol, PEG-4 laurate, iodopropynyl butylcarbamate and henoketiol.

Additionally, these, in combination with other essential oils, can offer sufficient protection for your cosmetic products. They are supposed to work in synergy with one another and mimic the activity of the synthetic preservatives. As formulations become more complex, these preservative systems may need to be altered or strengthened to give the same required results in the standard microbiological challenge testing program. 

Why Go for Alternative Preservatives to Meet Green Cosmetics Labels?


The influential factor in current formulation is the trend towards sustainability. Many green values will come together, like fair trade, sustainable sourcing, natural ingredients, organic raw materials, vegan sourced raw materials and more

Also, there is a need in response to give a meaningful and honest message to the consumers. The industry as a whole, still keeps missing the point and responding to the consumer's concerns with the usual explanation: Claiming naturals are made of chemicals, and chemicals can be safe or unsafe, either natural or synthetic.

Additionally, paraben alternatives like phenoxyethanol, MI/MIT… have failed to address the safety concerns of your cosmetic consumers. It’s time to rethink the strategy for regaining your consumers' trust by accelerating your switch to green alternatives process.

Switching to Natural Preservatives Alternatives to Meet Green Cosmetics Labels (EWG, COSMOS, Clean Beauty…)


Your Quest to Safe & Natural Cosmetic Preservation Ends Here

Your Quest to Safe & Natural Cosmetic Preservation Ends Here

Safe & Natural Cosmetic Preservation Synthetic preservatives are being scrutinized more every day as health hazards, irritants and just plain not good. Some are linked to various types of cancer while others are claimed to have some other potentially harmful side effects although the testing has not really shown that all synthetic preservatives fall into this category.

Yet the industry, in order to keep with the growing need for safer products is slowly trying to eliminate them from formulations. This will be a very slow process as the functionality of natural preservatives is obviously not the same as for their synthetic counterparts.

In searching for additional natural preservatives, suppliers are presenting more and more alternatives to the cosmetics formulator and several unconventional ingredients are being used. These new ingredients, although not truly considered preservatives by definition, have been tested to see if just by their chemical nature, they can function as microbe-killing ingredients. Many of them work in synergy with other ingredients while others strengthen the effect of some ingredients' already known natural bacteriostatic properties.

In searching for additional natural preservatives, we can see that it is an industry-wide process with many suppliers making these offerings. 


Much of the work involves simple (and sometimes complex) biochemistry and the understanding of the physical properties and functionality of the cells themselves. If an ingredient can alter the function of the cell membrane in a specific application, then it could be that the ingredient, when strategically placed in a formulation, might act with preservative-type properties.

Learn about some of the natural preservation options available today.

Essential Oils


They have antimicrobial activity and have been proposed as natural preservatives. The antimicrobial effect of essential oil depends on content, concentration and interactions between the main active compounds. Some of the common oils used include tea tree (Melaleuca alternifolia), thyme (Thymus vulgaris), lemon grass (Cymbopogon citratus), oregano (Origanum vulgare), rosemary (Rosmarinus officinalis), calamint (Calamintha officinalis) or lavender (Lavendula officinalis) and many others. View Several Essential Oil Grades with Antimicrobial Activity »

Mold, yeast, and bacteria are very abundant in the soil, breaking down dead plant tissue and supplying nourishment to the healthy ones. The ingredients obtained from plants have been determined to contain natural antibacterial properties.

So, we ask the question, can we use these same natural ingredients in cosmetic to serve this same function?
Is it legal if we do so?

The answer is yes to both questions.

The use of plants and plant extracts as natural preservatives is now very commonplace. Who would have ever thought that ingredients such as Aloe Vera, Grapefruit Seed Extract or Sorbitol would have these benefits? And there is no legislation that prohibits their use as anti-microbial agents.

Natural Preservatives Based on Alcohols


Rationally, they are synthetic molecules and some of them does or does not occur in nature. For example, propylene glycol does not exist in nature and naturally, it is derived from the fermentation of corn. It is used as a humectant but can also act as a preservative because of the -OH (hydroxyl) groups attached to the molecule making it function like an alcohol which by nature can act as anti-microbials.

Recommended products for preservation of natural cosmetics are discussed below.

  1. A-Leen® 5 (formerly called Pentiol Green +) by Minasolve
    • INCI: Pentylene Glycol; Use level: 0.5 >5.0%
    • Renewable alternative to petro-sourced Pentylene Glycol
    • 100% Derived-natural, Ecocert COSMOS approved

  2. E-Leen® 8 by Minasolve
    • INCI: Caprylyl Glycol (and) Glycerin (and) Aqua
    • Derived from sustainably sourced coconut and palm kernel oils
    • 100% vegetal, ECOCERT verified and COSMOS & NATRUE approved

  3. Zemea® Propanediol by Tate and Lyle
    • INCI: Propanediol
    • Preservative-boosting humectant which can replace petroleum-based glycols such as propylene glycol, butylene glycol and glycerin
    • Certified by NPS and considered organic ingredient under the definitions of ISO 16128-1

  4. Hydrolite® 5 green by Symrise
    • INCI: Pentylene Glycol
    • A by-product coming from sugar cane
    • 100% bio-based carbon, COSMOS approved


Organic Acids and Their Salt Derivatives


Moving further into the world of organic chemistry and functional molecules, we come across a wide variety of materials.

Propionic acid occurs naturally in grains, apples, strawberries and cheese salts of propionic acid sodium propionate, calcium propionate potassium propionate and myristyl propionate.

Benzoates are derivatives of benzoic acid and are natural preservatives which are tasteless and odorless, and which are used to extend the shelf life. Benzoic acid work best at a low (acidic) pH. It can be toxic in large amounts and can irritate the skin at high levels, which is true for any preservative. Don't forget, they are designed to kill microorganisms, so large amounts can be hazardous. Some common benzoate derivatives are calcium benzoate, potassium benzoate, sodium benzoate and benzyl benzoate.

Ascorbic acid is a vitamin which can be used as the organic salt of the acid. It exists in many plants but especially in citrus fruits. It can be used in both foods and cosmetics. It has excellent antioxidant qualities. Ascorbyl palmitate is a fat-soluble form of vitamin C that functions well in cosmetic oils and emulsions. Ascorbic Acid works better in water soluble products. Ascorbic acid is a non-toxic substance and does not irritate the skin. A large amount is needed for it to be effective in cosmetics. It works well when combined with Vitamin A (retinyl palmitate) and Vitamin E (tocopherols) to give broad-spectrum antioxidant activity. It protects against bacteria and some viral diseases. A cosmetic product that contains both ascorbic acid and ascorbyl palmitate is protected against microorganisms in both the oil and water phases of the product. Common forms are ascorbic acid, ascorbyl palmitate and magnesium and sodium ascorbyl phosphates.

Sorbic Acid and its salts of sodium sorbate, potassium sorbate and calcium sorbate. Also in common use is Acetic acid and its salts dehydroacetic acid and sodium dehydroacetate.  View Sorbic Acid and Its Derivatives Here »

Other ingredients act as preservatives by enhancing other natural preservative systems they are used in tandem with them to provide optimum antimicrobial effects with the elimination of conventional synthetic preservative systems. Such ingredients are gluconic acid, glucono delta lactone, glycereth-2 cocoate, C4-18 perfluroalkylethyl thiohydroxypropyltrimonium chloride, polyaminopropyl biguanide, caprylyl glycol, PEG-4 laurate, iodopropynyl butylcarbamate and henoketiol.

Additionally, these, in combination with other essential oils, can offer sufficient protection for your cosmetic products. They are supposed to work in synergy with one another and mimic the activity of the synthetic preservatives. As formulations become more complex, these preservative systems may need to be altered or strengthened to give the same required results in the standard microbiological challenge testing program. 

Why Go for Alternative Preservatives to Meet Green Cosmetics Labels?


The influential factor in current formulation is the trend towards sustainability. Many green values will come together, like fair trade, sustainable sourcing, natural ingredients, organic raw materials, vegan sourced raw materials and more

Also, there is a need in response to give a meaningful and honest message to the consumers. The industry as a whole, still keeps missing the point and responding to the consumer's concerns with the usual explanation: Claiming naturals are made of chemicals, and chemicals can be safe or unsafe, either natural or synthetic.

Additionally, paraben alternatives like phenoxyethanol, MI/MIT… have failed to address the safety concerns of your cosmetic consumers. It’s time to rethink the strategy for regaining your consumers' trust by accelerating your switch to green alternatives process.

Switching to Natural Preservatives Alternatives to Meet Green Cosmetics Labels (EWG, COSMOS, Clean Beauty…)


Methods to Test Antimicrobial Product Efficacy

Methods to Test Antimicrobial Product Efficacy

It is not only mandatory to add antimicrobials but also to test their efficacy after manufacturing and after storage until the expiration date.

Ability to test performance of the preservative efficacy test (PET), also known as the challenge test, is state of the art.

Today, more and more in-use tests are performed to simulate the usage by the consumer and to show efficacious protection against microbial growth after contamination. Various tests can be used to show the efficacy of antimicrobial products.

Challenge Test for the Efficacy of Preservation


The challenge test is used during product development to determine the efficacy and stability of the preservative system over time. The assessment is related to the stability of a formulation during manufacture, storage, and its use by the consumer, which includes:

  • Validation of the preservation efficacy when freshly prepared in laboratorial conditions,
  • Validation of the preservation efficacy after the end of storage in the container, to show possible interference with the packaging materials, and
  • Validation of preservation efficacy in the first production batch, just prior to packaging, thus revealing all possible influences occurring throughout the manufacturing process.

The test involves inoculating a measured amount of product with known amounts of microorganisms (bacteria, yeasts, and molds).

The challenge test consists in an artificial contamination of the tested sample and counting of the survivors during a period of 4 weeks maximum. The mortality rate is measured over this period in relation to the acceptance criteria set out in the official regulations documents.

The test method must be able to show the potential intrinsic antibacterial efficacy of a formulation and should thus be performed on each finished product in its intact original container as well.

Minimal Inhibitory Concentration (MIC) Test


The minimal inhibitory concentration (MIC) test principle is to determine the MIC of the test product by performing serial dilutions of the latter in growth medium and inoculating each dilution with the test strain. This test is very useful to compare activities of different products, products from the same category (e.g., soaps) with different actives, or the active ingredients themselves.

However, MIC data obtained on formulated products are very subjective and should be interpreted carefully. Usually, test organisms are Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli, for topical antimicrobial.
Minimal Inhibitory Concentration (MIC) Test by Performing Serial Dilutions
Minimal Inhibitory Concentration (MIC) Test by Performing Serial Dilutions


Zone Inhibition Test


The zone inhibition test method is largely used to test the resistance of bacteria to antibiotics. Antibacterial agents or products at different concentrations are applied to a substrate, a paper disk, or directly to the surface of an agar plate previously seeded with the test bacteria.

During the incubation, the test product will diffuse into the agar layer and produce a zone of growth inhibition of the micro-organism. The larger the inhibition zone, the higher the efficacy of the product. The strains used for this test are usually the same that those used for the MIC test. These two methods give a good idea of the bacteriostatic concentrations of the tested product or ingredient.

Checking the Antimicrobial Activity by Measuring the Zone of Inhibition
Checking the Antimicrobial Activity by Measuring the Zone of Inhibition


Time-Kill Test


The time-kill test determines both the killing kinetics and the activity spectrum of antibacterial formulations. This test is generally performed in suspension. The principle is to place in contact a dilution of the product or the antibacterial agent and a specified bacterial inoculum during a defined period of time.

Referral Test Methods


The following methods are commonly used in the cosmetic industry.

  • USP <51> Antimicrobial Effectiveness Testing (EP and JP)

  • PCPC (formerly CTFA) Microbiology Guidelines:
    • M-3 "A Method for Preservation Testing of Water-Miscible Personal Care Products"
    • M-4 "Method for Preservation Testing of Eye Area Cosmetics"
    • M-5 "Methods for Preservation Testing of Nonwoven Substrate Personal Care Products"
    • M-6 "A Method for Preservation Testing of Atypical Personal Care Products"
    • M-7 "A Rapid Method for Preservation Testing of Water-Miscible Personal Care Products"

  • IS0 11930 "Evaluation of the antimicrobial protection of a cosmetic product"

Methods to Test Antimicrobial Product Efficacy

Methods to Test Antimicrobial Product Efficacy

It is not only mandatory to add antimicrobials but also to test their efficacy after manufacturing and after storage until the expiration date.

Ability to test performance of the preservative efficacy test (PET), also known as the challenge test, is state of the art.

Today, more and more in-use tests are performed to simulate the usage by the consumer and to show efficacious protection against microbial growth after contamination. Various tests can be used to show the efficacy of antimicrobial products.

Challenge Test for the Efficacy of Preservation


The challenge test is used during product development to determine the efficacy and stability of the preservative system over time. The assessment is related to the stability of a formulation during manufacture, storage, and its use by the consumer, which includes:

  • Validation of the preservation efficacy when freshly prepared in laboratorial conditions,
  • Validation of the preservation efficacy after the end of storage in the container, to show possible interference with the packaging materials, and
  • Validation of preservation efficacy in the first production batch, just prior to packaging, thus revealing all possible influences occurring throughout the manufacturing process.

The test involves inoculating a measured amount of product with known amounts of microorganisms (bacteria, yeasts, and molds).

The challenge test consists in an artificial contamination of the tested sample and counting of the survivors during a period of 4 weeks maximum. The mortality rate is measured over this period in relation to the acceptance criteria set out in the official regulations documents.

The test method must be able to show the potential intrinsic antibacterial efficacy of a formulation and should thus be performed on each finished product in its intact original container as well.

Minimal Inhibitory Concentration (MIC) Test


The minimal inhibitory concentration (MIC) test principle is to determine the MIC of the test product by performing serial dilutions of the latter in growth medium and inoculating each dilution with the test strain. This test is very useful to compare activities of different products, products from the same category (e.g., soaps) with different actives, or the active ingredients themselves.

However, MIC data obtained on formulated products are very subjective and should be interpreted carefully. Usually, test organisms are Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli, for topical antimicrobial.
Minimal Inhibitory Concentration (MIC) Test by Performing Serial Dilutions
Minimal Inhibitory Concentration (MIC) Test by Performing Serial Dilutions


Zone Inhibition Test


The zone inhibition test method is largely used to test the resistance of bacteria to antibiotics. Antibacterial agents or products at different concentrations are applied to a substrate, a paper disk, or directly to the surface of an agar plate previously seeded with the test bacteria.

During the incubation, the test product will diffuse into the agar layer and produce a zone of growth inhibition of the micro-organism. The larger the inhibition zone, the higher the efficacy of the product. The strains used for this test are usually the same that those used for the MIC test. These two methods give a good idea of the bacteriostatic concentrations of the tested product or ingredient.

Checking the Antimicrobial Activity by Measuring the Zone of Inhibition
Checking the Antimicrobial Activity by Measuring the Zone of Inhibition


Time-Kill Test


The time-kill test determines both the killing kinetics and the activity spectrum of antibacterial formulations. This test is generally performed in suspension. The principle is to place in contact a dilution of the product or the antibacterial agent and a specified bacterial inoculum during a defined period of time.

Referral Test Methods


The following methods are commonly used in the cosmetic industry.

  • USP <51> Antimicrobial Effectiveness Testing (EP and JP)

  • PCPC (formerly CTFA) Microbiology Guidelines:
    • M-3 "A Method for Preservation Testing of Water-Miscible Personal Care Products"
    • M-4 "Method for Preservation Testing of Eye Area Cosmetics"
    • M-5 "Methods for Preservation Testing of Nonwoven Substrate Personal Care Products"
    • M-6 "A Method for Preservation Testing of Atypical Personal Care Products"
    • M-7 "A Rapid Method for Preservation Testing of Water-Miscible Personal Care Products"

  • IS0 11930 "Evaluation of the antimicrobial protection of a cosmetic product"

Perfect Preservative Selection Checklist

Perfect Preservative Selection Checklist

To make sure you make the right preservative selection, use the selection steps mentioned above and then double-check your selection using the checklist.

The Perfect Preservative Checklist
 Does the preservative provide broad-spectrum coverage?

 Does the preservative suit the organizational product philosophy?

 Does the preservative suit the pH of the finished product?

 Does the preservative have incompatibilities with any ingredients?

 Has the preservative been added at the appropriate temperature/method etc.?

Does the preservative provide broad-spectrum coverage?


Even if the product is at a low or high pH and therefore unlikely to grow certain types of microorganisms based on the environment, some microorganisms can still grow outside of their normal pH range.

It is therefore essential that you select a preservative system providing broad-spectrum coverage in all cases where product contains a high free water content.


Does the preservative suit the organizational product philosophy?


It is essential to make sure that your preservative suits the organizational philosophy otherwise it will not comply with the development requirements. Where there are conflicts with the required preservative and organizational philosophy, you will need to discuss this with the concept developer for further guidance.


Does the preservative suit the pH of the finished product?


Make sure you allow for pH drift which is a natural process over the shelf life of the product. Generally speaking, you should make sure that your preservative selection allows for at least a 10% pH drift (up or down) over the shelf life of the product.

For example, if your finished product is pH adjusted to 5.0, then the preservative you select should provide effective coverage to at least 4.5 - 5.5 to ensure it provides suitable coverage over the normal pH variances that occur throughout the shelf life of the product.


Does the preservative have incompatibilities with any ingredients?


If it does, it could be rendered ineffective. Make sure to thoroughly investigate the preservative system you are intending to use to check for any incompatibilities and if these apply to the product you are formulating.

Predict Preservative Compatibility Using HSP


Has the preservative been added at the appropriate temperature/method etc.?


Make sure you check how the preservative should be incorporated into your formulation, and ensure this is clearly stated in the formula by including it in the correct phase as well as written into the method below the formula.
  • Preservatives should be added to the water phase as early as possible during processing, but this is obviously not appropriate where:
    • Preservatives are not water-soluble, not suitable to be heated (if the product needs to be heated), or
    • The pH is not suitable – you don’t want to de-active your preservative by not following its required processing instructions!
pH and Temperature Adjustment
Make sure that the form of the preservative suits the form of the finished product, or can be incorporated easily, to ensure homogeneous distribution. Use a slurry method to disperse powders or add preservatives in liquid form to enhance more homogeneous distribution.

If the product is intended to be clear, make sure you have selected a preservative that will appear clear in the finished product.


Explore Various Preservatives Available for Cosmetics

View a wide range of preservatives available in the market today, analyze technical data of each product, get technical assistance or request samples.




About Dr. Barbara Olioso
Founder - The Green Chemist Consultancy

Dr. Barbara Olioso is a doctor of chemistry with a passion and scientific interest in plant botanicals and sustainability applied to cosmetic products. She is based in the UK and has been formulating and specialising in natural and organic cosmetics since 1999, developing skincare and haircare products. Back in 2005 she was behind the launch of the first certified organic eau de toilette with Primavera Aromatherapy, ie Espa International. Barbara also moderates the Sustainability Corner at In Cosmetics Global and writes on trade magazines.

Her services go from strategic technical support and project management for start ups and SMEs, to incorporate sustainability in NPD for bigger businesses as well as innovative and bespoke formulation services.

Dr. Barbara is author of The Green Chemist's Handbook for Cosmetic Preservation launched by her in 2021. This handbook is the result of her experience to help formulators save time and use green chemistry and "circular" cosmetic ingredients, free from parabens, phenoxyethanol and formaldehyde donors in their formulations.



References:
  1. Molecules: A Journal of Synthetic Chemistry and Natural Product Chemistry, 2018, Cosmetics Preservation: A Review on Present Strategies
  2. Cosmetic Microbiology, 2nd Edition, Philip A. Geis
  3. Handbook of Cosmetic Science and Technology
  4. Suppliers: Minasolve, Symrise, DuPont Tate & Lyle
  5. https://www.fda.gov.tw/TC/index.aspx

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4 Comments on "Cosmetics Preservation – An Ultimate Guide to Select the Right Preservative "
SANG JIN N Jan 25, 2022
Thank you for very useful information
Alicia F Dec 13, 2021
thank you for sharing this very helpful information.
Kay D Mar 20, 2020
Very helpful overview
Gloria A Sep 23, 2019
Excellent overview.

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