Prostaglandin D2 and histamine release in cold urticaria unaccompanied by evidence of platelet activation

Six patients with acquired primary cold urticaria and six normal control subjects were challenged with a 5-minute immersion of an arm in cold water, at 10 degrees C, to induce cold urticaria. Venous blood draining the arm was sampled before and at 5 and 20 minutes after challenge. Prostaglandin D2 levels in the serum increased significantly after cold challenge but did not correlate with the severity of the urticaria. Significant elevations in histamine after cold challenge tended to be higher in the patients with a low threshold to cold reaction. Two markers of platelet activation, platelet factor 4 and beta-thromboglobulin, remained at basal levels 5 minutes and 20 minutes after challenge.