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J. Cosmet. Sci., 57, 487-494 (November/December 2006) Development of a w/o/w emulsion for chemical peeling applications containing glycolic acid GULGUN YENER and AIDA BAITOKOVA, Istanbul University, Faculty of Pharmacy, Department of Pharmaceutical Technology, Cosmetics Section, Beyazit 34116, Istanbul, Turkey. Accepted for publication August 3, 2006. Presented as a poster, "Development of a new topical formulation for chemical peeling," at the Skin and Formulation Symposium, Paris, October 23-24, 2003. Synopsis Glycolic acid is a member of the AHA family, which occurs naturally in foods and has been used for centuries as a cutaneous rejuvenation treatment. It is used in many cosmetic products as an exfoliant and moisturizer. When glycolic acid is used in greater amounts, however, there are greater cosmetic benefits but also potential for skin irritation as far as burning increases. The aim of this work was to investigate the feasibility of a topical delivery system as a multiple emulsion combining glycolic acid, strontium nitrate, and dexpanthenol in order to optimize the acid's cosmetic properties and lowering its side effects. INTRODUCTION Glycolic acid (GA), a member of the hydroxy acid (AHA) family, is one of the most commonly used superficial chemical peeling agents, used to improve a variety of skin disorders. Recently it has proved to be a versatile peeling agent, and it is now widely used to treat many defects of the epidermis and papillary dermis in a variety of strengths ranging from 20% to 70%, depending on the condition being treated (1). Maintenance use of GA in low concentrations is effective for the control of various keratinization disorders, such as xerosis, ichtyosis, acne, and "age spot" keratoses. When used in high concentrations it causes epidermolysis, resulting in the regeneration of new epidermal and dermal tissue, and is beneficial for the treatment of actinic and seborrheic keratoses, warts, wrinkles, acne scars, and pigmentary changes such as postinflammatory hyper­ pigmentation and melasma (2,3). GA solutions with a concentration of more than 20% can only be used by dermatologists in practice, but GA is also available at lower concentrations as home-care products (4). Many reports have indicated that local appli­ cation of GA may induce varying degrees of sensory irritation (stinging, burning, and itching) reactions, especially at higher concentrations (5,6). The main problem related to GA in cosmetic applications is its irritative properties, and this generates the rationale for studies of cosmetic formulations with reduced adverse reactions. For this purpose, different types of microparticulate systems have been evalu­ ated: liposomes, liposomes modified by chitosan, and chitosan microspheres (7). Inves- 487