The pH of the human nail plate

In this chapter, measurements of the nail plate pH are reported. Measurements were conducted in vivo in 37 volunteers with healthy finger- and toenails, using a skin pH meter. The pH of unwashed and washed fin- gernails and the big toenails was measured, and the influence of washing, anatomical site (fin- gers/toes), side (left/right), finger digit (digits 1–5), and gender were determined. The pH of the nail plate surface was around 5. There was no significant difference between the sides, i.e., the right or left hand/foot, among the ten fin- gernails and between the two great toenails. However, toenails had a significantly higher pH than fingernails. Washing the nails caused an immediate, but transient, increase in pH, which was not sustained with time, and pH returned to prewashing levels within 20 min. In males, washing did not significantly influ- ence finger- or toenail plate pH. In females, however, washed fingernails had a signifi- cantly higher pH than unwashed ones, while there was no difference in the pH of the toe- nails. The pH of the nail plate interior, mea- sured after tape stripping, was found to be slightly lower than that at its surface.