Skin surface and open comedone pH in acne patients.

To assess the variability of surface and comedone pH in one and the same individual and between individuals, pH measurements were made on extracted single comedone material and on the adjacent skin surface, at face and back sites on 56 acne patients. The pH values were normally distributed. The mean values were: comedone pH 5.52 and surface pH, 5.26. The pH ranges were similar: comedones 4.01 to 6.85 and surface, 4.10 to 6.81. There was no correlation between comedone pH and adjacent skin surface pH. On each person and at one site there was variability of surface pH and comedone pH. Variability of pH from person to person was greater than within an individual at the same site.