Effects of Topical Salicylic Acid and Erythromycin on the Erythema Induced by UVB

Objective: Various studies have shown blocking or enhancing effects of topical agents on UVB penetration. Since the lesions in acne vulgaris are frequently localized on sun exposed areas, the interaction between topical agents used in acne treatment and UVB is important. In this study, our purpose was to examine interactions between UVB and salicylic acid gel, erytromycin gel which are frequently used in the topical treatment of acne vulgaris. Material and Methods: In thirty-three volunteers, a phototest was performed to determine the minimal erythema dose (MED) and the test was repeated with gel forms of 2% salicylic acid, 2% and 4% erythromycin applied as a thin (0.1 cc/25 cm) and a thick (0.3 cc/25 cm) layer. After 24 hrs, the effects of each agent on MED was investigated. Results: The topical application of thin and thick 2% salicylic acid gel significantly increased the MEDs. On the other hand, thin application of 2% and 4% erythromycin gel, and thick application of 4% erythromycin gel significantly decreased the MEDs. Conclusion: It can be advised to use erythromycin gel carefully for acne lesions in day time due to its possible enhancing effects of erythema of UVB.