A wide range of surfactants have been developed as milder alternatives to more traditional systems for personal care cosmetics. John Woodruff looks at some of the benefits they offer
"Arguably surfactants are the single most important class of compounds found in cosmetics." So begins an essay question set by the Society of Cosmetics Scientists (UK) in its prestigious distance learning course. It is a statement that is difficult to dispute as they are used as cleansing and foaming agents, emulsifiers and solubilisers, for the wetting and dispersal of pigments, and for skin and hair conditioning. In addition, they may have antimicrobial properties, add emolliency, modify product rheology, and impart texture and feel to product compositions.
This feature looks at the mild surfactants used in personal cleansing formulations, as well as some of the more recently introduced emulsifiers and solubilisers, and thickening aids for systems that do not respond well to the addition of electrolytes.
Shower gels and body washes are invariably based on surfactants and the well established combination of sodium laureth sulphate (SLES) with cocamidopropyl betaine (CAPB) is still the most common in use. However, for more expensive brands with claims of extra mildness, creamier foams and other positive attributes, there are many more materials to investigate. The pursuit of more mild compositions may have been stimulated by a paper by Peter Dykes published in the International Journal of Cosmetic Science (IJCS) in 1998.
In it Dykes described the effects of surfactants on the skin and wrote that when we clean the skin we remove not only the bacteria, dirt and grease which have accumulated but also part of its natural barrier, the stratum corneum. Corneocytes, both singly and in clumps, are released from the skin’s surface by the action of detergents and mechanical stimulation. So too are the lipids and proteins which make up the inter-corneocyte region of the stratum corneum. Changes in the physical properties of skin occur after washing. For example, changes in skin-surface pH and transepidermal water loss (TEWL) are easily demonstrable. Also excessive exposure to surfactants results in repeated damage to the stratum corneum which can in turn lead to irritant dermatitis.