Females have lower skin surface pH than men - A study on the influence of gender, forearm site variation, right/left difference and time of the day on the skin surface pH

Background/aims: It is of great interest to describe the many functions and properties of the skin in order to better understand reactions that result in different skin abnormalities, as a prerequisite in the development of skin products and topical medicines. Skin surface pH is considered a critical parameter of skin wellbeing and is typically studied on the forearm skin. Despite many previous investigations, this is an extensive field that still needs a great deal of research. The aim of our study was to investigate gender related differences, differences between right and left arms, anatomical variation and daytime variation in skin surface pH. Methods: Skin surface pH was measured on the flexor surface of the forearm on eleven healthy volunteers (6 men and 5 women). A Mettler Toledo pH meter (pH meter 1140) was used. The subjects were measured once every hour from 8 a.m. to 3 p.m. in five areas from the elbow to the wrist. In each of the five areas, three measurements were performed next to each other, and the mean of these was used in subsequent calculations. Results: A statistically significant difference in skin pH between men (mean pH=5.80) and women (mean pH=5.54) was found, with women being more acidic than men (P<0.01). No difference between right and left arm was found. In men, the area closest to the wrist had significantly lower pH values compared with the proximal sites. This was not the case in women. Skin surface pH decreased during normal working hours in both genders. Conclusion: Spontaneous skin surface pH was found to be significantly lower in women, as compared to men - albeit, the difference was small and of unknown relevance. Nevertheless, comparative studies on skin surface pH should be balanced with respect to gender. There appeared to be no right/left difference and no systematic change during the working day. Also, measurements should not be conducted close to the wrist.