Surfactants in Skin and Hair Products

The word surfactant is a shortened form of "surface-active agent", a surfactant is a chemical that stabilizes mixtures of oil and water by reducing the surface tension at the interface between the oil and water molecules. Because water and oil do not dissolve in each other, a surfactant has to be added to the mixture to keep it from separating into layers. Surfactants in cosmetics provide one or more of six different functions:

  • Detergents for cleansing
  • Wetting agents in perms
  • Foaming agents for shampoos
  • Emulsifiers in creams and lotions
  • Conditioning agents in skin and hair-care products
  • Solubilizers for perfumes and flavors
Woman shampooing her hair
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Detergent: Cleansing surfactants include soaps and detergents that are placed on the skin or hair for cleansing purposes. These surfactants will draw the oil to the surfactant. Then, when the surfactant is rinsed away while holding onto the oil, the oils are rinsed off with the water.

Foaming agents: Many products such as cleansers or shampoos are often available in a foam form as opposed to a liquid form. Studies have shown that consumers often prefer the foam formulation, although the fact that it is a foam does not necessarily have anything to do with its ability to clean. One example of a foaming face wash is the Cetaphil Oil-Control Foaming Face Wash. The surfactant in the foaming agent allows the product to remain as a foam as opposed to collapsing back into liquid form. Certain topical medications such as topical steroids (e.g. Olux foam) or topical minoxidil are also available in foam formulation. These foam formulations are sometimes preferred by patients when applying a medication to the scalp.

Emulsifiers: Emulsions are mixes of oils and water that are semi-stable and do not separate out into their oil and water layers. The surfactant allows the emulsion to have this well-blended quality. Examples of emulsions are moisturizing creams and lotions. Consumers generally prefer moisturizers to be of uniform texture as opposed to layers of oil and water or just the oil itself. When applied to the skin, the oils are "delivered" to the skin surface.

Conditioning agents: Conditioning agents include "leave-on" skin and hair-care products such as hair conditioners. After using a hair conditioner, the product remains on the hair, giving it a smooth feel due to the lipophilic (oily) portion of the molecule.

Solubilizers: Surfactants may be used as solubilizers when attempting to try to blend a small amount of oil into a large quantity of water. An example of products include colognes, perfumes, and skin toners.

The Chemical Makeup of a Surfactant

Since surfactants stabilize mixtures of oil and water, they have both a hydrophilic ("water-loving") and lipophilic ("oil loving") groups. Having both these groups makes the surfactant amphiphilic. The hydrophilic group allows the surfactant to be soluble in water while the hydrophobic group allows the surfactant to be soluble in oils.

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By Heather L. Brannon, MD
Heather L. Brannon, MD, is a family practice physician in Mauldin, South Carolina. She has been in practice for over 20 years.