Suppression of epicutaneous reactivity by terfenadine and loratadine.

We compared the relative antihistaminic effects of loratadine (10 mg), terfenadine (120 mg), and placebo in patients with tree pollen-induced allergic rhinitis. Wheals were produced by epicutaneous tests with serial dilutions of histamine phosphate, tree and grass pollen extracts before ingestion of medication. Repeat tests were performed after seven days of treatment. Terfenadine was more effective than both loratadine (P less than .01) and placebo (P less than .001) at suppressing histamine induced wheals. Terfenadine was more effective than placebo (P less than .01), but not loratadine at inhibiting both tree-induced and grass-induced epicutaneous reactions. In this study, terfenadine was more potent than loratadine in inhibiting both histamine-induced and allergen-induced epicutaneous wheals.