x -HYDROXY ACIDS IN COSMETOLOGY

Yasemin YAZAN*°

*Anadolu University, Faculty of Pharmacy, Department of Pharmaceutical Technology, Department of Cosmetology, 26470 Eskisehir, TURKEY.
°Corresponding Author

Summary:
x- Hydroxy acids are the organic acids which contain one or more hydroxyl groups on their carbon chain and which are included nowadays in almost every cosmetic preparation. Purposes of incorporating them into cosmetic preparations are their hydration efficacy at low humidity medium, obtention of brilliant and smooth appearance by reducing skin pigmentation and wrinkles. a-Hydroxy acids (AHAs) present their cosmetic efficacy due to the reduction in stratum corneum thickness and improvement in hydration caused by diminishing the cohesion of the dead cells of stratum corneum and by leading to the removal of dead surface cells. Mechanisms of action and the possible efficacies of AHAs with different structures vary depending on their penetration, disposition and remaining time on stratum corneum, and amount and region applied. Selection of AHA and pH of the formulation are important issues in formulating AHAs for cosmetic purposes. Effect of addition to the texture of the outermost layer of skin is increased when the AHA's length of carbon chain is shorter; on the contrary, moisturizing property is increased when the chain is longer. AHAs are present in formulations partially neutralized by such materials as triethanolamine, sodium hydroxide, ammonium or sodium lactate. Besides the classical systems like solutions, lotions, creams and gels, novel delivery systems are being utilized in formulations. AHAs, which are widely used for skin hydration, removal of age spots, inhibition of formation of comedones and for superfacial exfoliation, can be applied to regions such as palms, scalp or large body surfaces of individuals who suffer skin dryness, flakiness and roughness.
Issues on their long-term effects, efficacy either alone or as a complex and efficacy of different a-hydroxy acids related to their structures have not gained certainty. In this review, pharmacological and technological properties and use of a-hydroxy acids have been summarized.

Key words:
x-Hydroxy Acids, Formulation, Pharmacological Activity, Cosmetic Use