The proposed use of H2-receptor antagonists in urticaria and atopic dermatitis.

To the Editor.— Over the past few years, it has been learned that H2-receptor sites exist on peripheral vascular walls and on the surface of lymphocytes (possibly polymorphonuclear leukocytes and macrophages as well). Grennan et al demonstrated effective H2-receptor blockade of xenon clearance from histamine-treated canine diarthrodial joints, a model providing indirect measure of synovial perfusion.1Fermont et al found in human skin that pyrilamine (an H1-antagonist) and metiamide (an H2-antagonist) provided significantly greater suppression of histamineinduced flares than mepyramine alone.2 Histamine uptake by tuberculinsensitized lymphocytes could be blocked by metiamide, suggesting H2-receptor sites on these cells.3Histamine inhibition of T-lymphocyte mediated functions could be effectively blocked with H2-antagonists.4Cimetidine enhancement of delayed hypersensitivity responses in skin has been shown.5 Based on the above data, H2-antagonists may be expected to have