Citric acid increases viable epidermal thickness and glycosaminoglycan content of sun-damaged skin.

Background: Recently, there has been an exponential increase in the use of alpha-hydroxy acids in dermatologic practice. Their inclusion in a myriad of cosmetic preparations underscores their popularity. Among the clinical effects of alpha-hydroxy acids are their ability to prevent the atropy resulting from potent topical corticosteroids, improve the appearance of photoaged skin, and correct disorders of keratinization. Despite this range of desirable effects, very little is known about the specific changes produced by various alpha-hydroxy acid preparations in the epidermis and dermal extracellular matrix. Previous work by others has demonstrated the ability of another alpha-hydroxy acid to increase viable epidermal thickness, and dermal glycosaminoglycans.
Objective: In this study, we examined the effect of 20% citric acid lotion, as compared with vehicle alone, on skin thickness, viable epidermal thickness, and dermal glycosaminoglycan content. Biopsy samples were harvested after 3 months of treatment.
Results: Image analysis of biopsy sections revealed increases in viable epidermal thickness and dermal glycosaminoglycans in treated skin.
Conclusions: Topical citric acid produces changes similar to those observed in response to glycolic acid, ammonium lactate, and retinoic acid including increases in epidermal and dermal glycosaminoglycans and viable epidermal thickness. Further studies of citric acid and other alpha-hydroxy acids are warranted to clarify their clinical effects and mechanisms of action.