The pH of commercially available rinse-off products in Sri Lanka and their effect on skin pH.

INTRODUCTION: Initially linked to antimicrobial function, the acidic skin pH plays a key role in permeability barrier homeostasis and integrity of the stratum corneum. Barrier recovery is delayed when acutely perturbed skin sites are exposed to a neutral pH. OBJECTIVE: To evaluate the pH of commercially available rinse-off products in Sri Lanka, and the effect of detergent rinses on skin pH and its recovery rate. METHODS: The pH of 18 rinse-off products was determined using pH indicator paper and a pH meter. The effect of an alkaline (pH 9) and an acid (pH 5.5) rinse-off product on the hand skin pH was compared in 48 healthy volunteers after single and multiple applications. The skin pH of the dorsum of hands was measured in nurses before (n = 131) and during (n = 40) a duty shift that involved frequent hand washing using alkaline soap. RESULTS: Soaps available in Sri Lanka have a pH of 9.1-10.5. The pH of syndets and cleansers range from 5.5-7.0. Five minutes after hand washing, the mean skin pH increased by 1.7 +/- SD 0.5 pH units with alkaline soap, and by 0.8 +/- SD 0.4 pH units with acidic cleanser (p < 0.0001). Recovery of pH was slower when alkaline soap was used. The increase in skin pH was significantly greater when hands were repetitively washed with alkaline soap (p < 0.0001). The mean skin pH values of nurses before (4.9 +/- SD 0.4) and during (5.7 +/- SD 0.7) the work shift were significantly different (p < 0.0001). CONCLUSIONS: Alkalinisation with rinse-off products increases the skin pH with potential functional and clinical implications.