From the skin to the thyroid: immunological mechanisms and therapeutic implications of the comorbidity between chronic spontaneous urticaria and autoimmune thyroid disease

Chronic spontaneous urticaria (CSU) is the most common subtype of chronic urticaria, characterized by recurrent wheals and pruritus without identifiable triggers. CSU is a complex autoimmune skin disease, and patients with type I and type IIb autoimmune subtypes frequently have comorbid autoimmune thyroid diseases (AITD), such as Hashimoto’s thyroiditis (HT), suggesting shared immunological mechanisms between the two conditions. This article systematically reviews the epidemiological characteristics, multidimensional pathogenesis, and advances in clinical diagnosis and treatment strategies for CSU–AITD comorbidity. We focus on the roles of thyroid autoantibodies, immunoglobulin E (IgE)-mediated immune responses, and the complement system in disease progression, highlight the controversial mechanisms linking the two conditions and their therapeutic implications, summarize current treatment strategies targeting the comorbidity, and explore whether thyroid antibodies represent a causative factor or merely an epiphenomenon.