Multicenter study on measurement of the natural pH of the skin surface

Characterization of the skin's natural state is very important for understanding skin functions and describing disturbances of skin function. In the field of cosmetics and dermatologicals the natural pH of the skin surface plays an important role in the development of products with a skin neutral pH. In a multicenter study the natural pH of the skin surface (exception of underarm and genital areas), was to be measured. It was to be determined whether gender-specific differences in the pH occur. The skin surface pH was measured on the inside of the forearms in 222 volunteers (147 female, 75 male) using the skin pH meters of the respective institutes. The pH was measured in triplicate on adjacent areas 24 h after the last contact of the measuring site with water, topical applications and an intensive washing procedure. The values of the skin surface pH were 4.9 (arithmetic mean). The 95% interval was between 4.1 and 5.8. The pH on the forearm of the male volunteers was slightly lower than that of the females. The difference was statistically significant (p < 0.01; 4.8 to 5.0). The authors suggest that the GDCh recommendations for the claims »skin neutral pH«, »ideal pH« or »skin-friendly pH« should be revised and propose a pH range of 4.1 to 5.8 for the main body areas excluding the underarm and genital areas.