Chronic urticaria Investigations with patch and challenge tests.

56 patients with chronic urticaria were patch tested with particular reference to the immediate weal response to a range of materials and this was followed by challenge tests to most of the same substances. Positive immediate patch tests were commonly seen with balsam of Peru and cinnamon and this appears to be a reaction in many normal subjects. Positive challenge tests in patients who also had positive immediate patch tests to the same substance occurred in two patients with cinnamon and two patients with cloves. Other substances with a similar action may come to light, in which case the use of immediate patch tests in investigating chronic urticaria is more likely to be of value. 4 patients showed positive immediate patch tests to nickel, one of whom also had a positive 48 hr patch test to nickel. 2 other patients had only positive 48 h patch tests to nickel. However, none of these patients gave a positive challenge test to nickel.