Skin surface pH, moisture, and pruritus in haemodialysis patients

Pruritus is one of the most common complaints of haemodialysed patients. However, its pathogenesis remains unclear. Dryness of the skin and the effects of pH changes on the nerve endings in the skin have been suggested as related factors. In the present study we measured skin pH using a skin pH meter and skin moisture using a corneometer at four different sites in 41 haemodialysis patients, before and after dialysis, and in 40 healthy controls. Thirty patients (73%) complained of pruritus, six severe constant, 12 moderate and 12 mild. Skin surface pH was higher in patients than in controls in the upper back (5.54 +/- 0.14 versus 5.22 +/- 0.08, P < 0.02), forearm (5.5 +/- 0.1 versus 5.13 +/- 0.1, P < 0.01) and forehead (5.35 +/- 0.08 versus 5.04 +/- 0.07, P < 0.004), whereas there was no difference in the axilla. Haemodialysis had no effect on skin pH, and there was no correlation with blood pH, blood bicarbonate and serum electrolytes. There was no correlation between skin surface pH and pruritus. Skin moisture was lower in haemodialysis patients than in controls in the forehead and axilla. There was no correlation with pruritus. Skin surface pH is higher in haemodialysed patients than in healthy controls in most areas of the body, despite the fact that these patients have a decreased blood pH. Thus, the skin pH is not related to systemic acid-base balance. It is possible that the uraemic state affects the ability of the dermal cells to secrete acid, making the skin more susceptible to bacterial and fungal infections.(ABSTRACT TRUNCATED AT 250 WORDS)