In addition to histamine, leukotriene C4 (LTC4) might also play a role in mediating cold urticaria wheals. To study the significance of LTC4 vs. histamine, 6 patients with cold urticaria were challenged with the ice cube test before and after ingestion of 10 mg cetirizine (antihistamine), 10 mg montelukast (leukotriene antagonist) or a combination of both drugs. Cetirizine diminished the cold-induced wheal by 50 +/- 42%. Montelukast had no significant effect, and the combination of both drugs diminished the wheal by 37 +/- 33%. Furthermore, a skin microdialysis technique detected the release of histamine in the cold-induced wheal, whereas no LTC4 release was detected. In conclusion, the antihistamine is effective and histamine is released, whereas the leukotriene antagonist is not effective and LTC4 is not released in the cold urticaria wheal.