UV treatment of uraemic pruritus reduces the vitamin A content of the skin.

The effect of phototherapy on uraemic pruritus and vitamin A content in serum and epidermis was investigated in ten patients with chronic renal failure. The patients and five healthy controls were given repeated whole-body irradiation of UV-A + UV-B (total dose 7.9 + 1.3 J cm-2). Serum and skin samples were obtained before and after the treatment. Serum samples were analysed for retinol, retinol-binding protein and carotene and epidermis samples for retinol, 3-dehydroretinol and carotene. Before treatment, the retinol concentrations in serum and epidermis were higher in patients than in controls. The treatment, which relieved seven patients of pruritus, reduced the epidermal retinol from 11.6 +/- 4.5 to 7.0 +/- 3.8 nmol g-1 protein (P less than 0.02). A similar reduction occurred in the controls (4.5 +/- 1.0 v. 1.7 +/- 1.0, P less than 0.01). No changes of epidermal 3-dehydroretinol, carotene or the serum parameters occurred in either patients or controls. The putative relationship between uraemic pruritus and hypervitaminosis A and the response of this condition to UV therapy is discussed.