Disclosed is a rapid, non-invasive and highly specific and sensitive diagnostic assay for the identification of individuals with autoimmune chronic urticaria, which makes use of CD203c, and in some embodiments, additional proteins, as a marker for the disease. Test kits for diagnosis of an individual suspected of having autoimmune chronic urticaria are also disclosed. Also disclosed are a method of identifying compounds useful for treating autoimmune chronic urticaria and a method of treating autoimmune chronic urticaria.