Background: defining the etiology of chronic urticaria is difficult and complicated. This study designed to define the prevalence of CM allergy in patients with chronic urticaria and determine the efficacy of Sublingual immunotherapy for patients with chronic urticaria allergic to CM. Method: 147 patients (mean age 34.3 years, 60 males) with chronic urticaria after exclusion of systemic diseases underwent skin prick test then complete restriction of CM for 2 weeks then open challenge with CM to determine the prevalence of CM allergy in those patients. Only patients with complete remission of symptoms with milk elimination and re-appearing of symptoms with re- challenge are diagnosed to have CM allergy. After that patients who diagnosed to have CM allergy submitted to 6 weeks of sublingual immunotherapy for CM then re-challenged with CM to determine the efficacy with this modality of therapy. Results: 53 patients (36%) diagnosed to have CM allergy by the diet elimination and re-challenge test. From the 53 patients 51 agreed to administer Sublingual immunotherapy for CM. After the 6 weeks another 2 patients dropped out through the follow up and 49 patients completed the trial to the end; from those 34 patients (69%) showed complete remission after re-challenge with CM and maintained that remission for another 2 months follow up 32 (60.4%) maintained on remission after 1 year and 31 (58.5%) maintained after 3 years. Conclusion: CM allergy is an important cause of chronic urticaria, and theSublingual immunotherapy for CM is the promising way to treat that group of patients proved to have CM allergy.
