The effect of nedocromil on weal reactions in human skin.

1. Nedocromil 2% iontophoresed into human skin had no effect on wealing produced by intradermal histamine, 48/80 or house dust mite antigen. 2. Iontophoresis of 0.002-2% nedocromil itself resulted in dose-related wealing. 3. This wealing was reduced by 62 +/- 8% s.e. mean by the H1-receptor antagonist terfenadine which decreased histamine wealing by 68 +/- 2% s.e. mean. 4. Nedocromil may therefore act as a weak agonist on a skin mast cell receptor concerned with histamine release.