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Select Preservatives for Cosmetics

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, 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.

Why Preservation is Important?


TAGS:   Preservatives    

Preservatives for CosmeticsSeveral products in the market contain ingredients which make cosmetic systems very difficult to preserve. For example, personal care products contain significant amounts of water and other ingredients that may be susceptible to contamination by microorganisms like bacteria, fungi, and molds.

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

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. However, one also must be careful with over-preserving a product as too much preservative in a product is not good either.


Let’s find out what are the different preservation chemistries available & criteria to select the right preservation…


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Preservative Chemistries


Preservatives have different ways of working based on their chemistry. Some common types of preservatives used in cosmetic formulations with their features are:

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
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

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. Careful preservative selection is essential to make sure the preservative/blend provides broad-spectrum protection and is suited to the product being created.

While speaking of it looks easy, formulating with preservatives can sometimes be very difficult. Find out how to make the perfect preservation selection…


Criteria to Select the Right Preservative


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

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…

  1. Company/ Product Philosophy
  2. Regulatory Considerations
  3. Product Form
  4. pH
 

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#1 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.

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?


#2 Regulatory Considerations


Regulatory Considerations for Preservatives
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.

Limits 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.


#3 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

#4 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.


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:
Perfect Preservative Selection Checklist


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.



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Green Preservatives for Cosmetics


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1 Comments on "Select Preservatives for Cosmetics"
Gloria A Sep 23, 2019
Excellent overview.

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