The effect of H1 and H2 blockade on cutaneous histamine response in man.

Histamine-induced cutaneous wheal responses were measured in 10 healthy subjects. The effect of the potent H1 blocker, hydroxyzine HCl, the H2 blocker, cimetidine, and the two drugs in combination was determined. The H1 blocker alone produced a mean wheal suppression of 75% (p less than 0.001). The H1 plus H2 blocker produced 84% suppression. The augmented suppression of H1 plus H2 blocker vs H1 blocker was statistically significant (p less than 0.02). The H2 blocker alone produced suppression that was not statistically significant. The results provide additional evidence that H2 receptors are present in the human cutaneous microcirculation, and add support to the clinical observation of therapeutic efficacy of H1 plus H2 blockers seen in some patients with chronic urticaria.