Surfactants in Skin Care and Make-Up Applications

Surfactants are an essential part of most skincare and make-up products. In skin care applications, they are used as emulsifiers for the production of creams and lotions. In body washes, surfactants act as the cleansing agent to lift the oil-based dirt and contaminants from the skin. They are also used as thickeners, gelling agents, and film-forming agents in various make-up applications.

Creams and Lotions

Creams and lotions may be used as a medicine delivery system or to smooth, soften, moisturize, and perfume the skin. Both types of products are a mix of water and oil-based ingredients combined into a homogenous product through the use of emulsifiers.

Lotions have a higher percentage of water than creams. They consist of tiny droplets of oil suspended in an aqueous medium. Lotions are more easily absorbed into the skin and tend to be less greasy and lightweight. Creams contain a higher percentage of oils than lotions. They are also known as water-in-oil emulsions as they consist of tiny droplets of water suspended in an oil base. Creams are heavier and richer than lotions. They are used to form a barrier which keeps the skin hydrated. The choice of a suitable emulsifier depends on the ratio of water and oil-based content. The emulsifier must also have low toxicity, low irritancy, and good dispersibility.

Polyethylene glycols (PEGs) are widely used as a base for cosmetic creams and lotions. They are petroleum-based compounds also used as softeners, thickeners, solvents, and moisture carriers in cosmetic applications. PEGs have low toxicity and mild irritancy. They are easily soluble in water and have a broad compatibility with various substances. PEGs are also used as anticaking agents. In cosmetics, PEGs are used as emollients to help soften and lubricate the skin, as emulsifiers, and as penetrating vehicles to deliver other active ingredients deeper into the skin.

Body Washes

The purpose of a body wash is to gently remove dirt, contaminants, and odor from the skin. A surfactant is the key component in a body wash. The primary job of the surfactant is to clean the skin by removing lipophilic dirt and natural oils from the skin. Surfactants have a hydrophilic, polar head group and a lipophilic, non-polar tail. The surfactant molecules assemble into micelles which are spherical aggregates in which the hydrophilic head groups are in contact with the polar solvent (water), and the hydrophobic tails extend into the center of the micelle. Dirt and oils are trapped in the core of the micelle while the hydrophilic outer surface keeps the micelle suspended in wash water.

The body wash surfactant must also generate fine foam to cover a larger surface area and deliver a more fulfilling user experience. Body washes are generally formulated to be viscous liquids with a pH in the range of 6 to 7. A suitable surfactant must therefore be able to produce a large amount of foam even under acidic conditions. It should have low irritancy and must not cause excessive degreasing which may lead to skin irritation. A body wash formulation may include more than one surfactant. A secondary surfactant may be added to control skin irritation and reduce discomfort.

Make-up Applications

Some surfactants also act as thickeners, gelling agents, and film-forming agents in various cosmetic products. Acting as thickeners or gelling agents, they enhance the consistency, volume, stability, and viscosity of the product. They enhance the ability of the product to retain water on the skin and therefore act as moisturizers.

Selecting the Right Surfactant for Cosmetics