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Among the AHAs, the short-chained glycolic acid is reported to be the most effective by one group of researchers, while another group claims the better efficacy of the complex forms of AHAs. To begin with, glycolic acid has been formulated as a multiple emulsion which is known as a vesicular system with good consistency and homogenity to be applied directly to the skin and to release the active agent in a sustained pattern.
Following formulation, characterization, stability and rheological studies of the simple and multiple systems, skin pH, sebum, moisture and elasticity was determined at a 4-week period after application of the multiple emulsion to 10 volunteers.
The multiple system prepared seems to add to the elasticity, moisture and sebum of the skin and keeps the skin at the low acidic range for the 4-week period.
INTRODUCTION
alpha-Hydroxy acids (AHAs), reported for cosmetic use for the first time in 1974 (1), are considered renaissance materials. However, their long-term usage and their formulation are still under discussion. AHAs, beginning with the simplest structured acid, glycolic, lactic, tartaric, citric, malic, mandelic, benzylic and gluconic, are introduced into cosmetic products either alone or as a complex (2).
AHAs are used for the long-term control of dry skin, ichtiyosis, acne, age spots and superficial wrinkles and for increasing the elasticity of the skin, at low concentrations (6). The choice of the AHA and the concentration of the free acid are the two critical points in the cosmetic formulation of AHAs (7).
Depending on the type of AHA, its concentration, delivery system, application period and other conditions, it is reported to lead to the synthesis of new collagen (8).
AHAs have been used in antiaging and exfoliating preparations as well as men's, ethnic and nail cosmetic products (9,10, 11).
Multiple emulsions are promising delivery systems in cosmetics in the sense of encapsulating various substances for masking malodors and bad taste of the active ingredient, protection from the environmental conditions, maintaining the sustained release of the material incorporated and formulation of the hydrophilic and lipophilic and/or incompatible materials together (12, 13, 14, 15).
The purpose of this study was to formulate glycolic acid as a multiple emulsion system and to evaluate the physical, rheological, microbiological and dermatological characteristics of the system.