An assessment of the human nail plate pH.

PURPOSE OF STUDY To measure the pH of the surface of healthy nail plates. PROCEDURES The surface pH of human fingernails and big toenails was measured in vivo using a skin pH meter. The influence of washing, anatomical site (fingers/toes), side (left/right), digit (digits 1-5) and gender was determined. The pH of the nail interior was also measured. RESULTS The pH of the nail plate surface was around 5, with toenails having a significantly higher pH than fingernails. Immediately after hand washing, the nail surface pH increased significantly, from pH 5.1 ± 0.4 to 5.3 ± 0.5. However, this was not sustained with time, and the pH returned to prewashing levels within 20 min. Gender had an influence on unwashed, but not washed, nail plate pH. The pH of the nail plate interior was lower than that of its surface. CONCLUSIONS It was possible to measure nail plate pH, and baseline values are provided.