The sensitivity of uremic and normal human skin to histamine

Cutaneous reactions induced by intradermal histamine injection were studied in uremic patients with and without pruritus who were undergoing maintenance hemodialysis and also in healthy subjects. Flare reactions were significantly smaller in both groups of patients than in controls. However, the itch responses following histamine injection were greater in patients with pruritus than in non-pruritic patients and healthy subjects, indicating an augmented sensitivity to pruritogens in these patients. The development of histamine tachyphylaxis was demonstrated in healthy human skin. After repeated histamine injections at intervals of 90 min, both itch and flare responses decreased rapidly. A similar decline in histamine reactivity occurred when the interval between injections was extended to 24 h. The phenomenon of histamine tolerance was confirmed in 2 uremic patients.