Effects of local corticosteroids on acute experimental urticaria.

Corticosteroids are often used in the treatment of acute or chronic urticaria. However, their effects on mastocyte activation as well as on the histamine-induced dermal oedema remain poorly investigated. The aim of the present study was to investigate the effects of corticosteroids (CS) on the development of acute experimental urticaria induced by prick-tests with histamine and codeine. This experimental model corresponds to the common form of urticaria. CS were administered at the site of the histamine and codeine prick tests in order to test for a direct effect on the development of acute urticaria. Two types of experiments were performed: 1) after a 48-hour period of topical CS application on the forearm, 7 healthy volunteers were skin prick-tested with histamine and codeine simultaneously in duplicate, one series in the pretreated area and the other in a non-treated area. 2) six other volunteers were prick-tested with histamine and codeine on their forearm, in duplicate. Immediately after testing, intradermal methyprednisolone was injected at the site of the prick-tests in the last series. Skin wheal and flare responses were measured after 20 mns and statistically compared with and without CS treatment. Whereas short-term CS topical application did not appear to modify cutaneous reactivity to histamine and codeine, local CS injection was associated with a significant increase in the flare induced by histamine and codeine (respectively + 18 +/- 3% and + 38 +/- 3%; P = 0.05). The wheal tended to be increased after injected CS. In conclusion, these results show that CS are neither able to prevent nor to improve experimental urticaria, i.e. wheal and flare, and even increase the histamine and codeine-induced erythema. That a similar result could apply to patients with chronic urticaria and with systemic CS remains to be studied.