Chronic inducible urticaria: classification and prominent features of physical and non-physical types

Chronic inducible urticaria (CIndU) is a common inflammatory skin condition characterized by the recurrence of itchy wheals and/or angioedema that lasts more than 6 weeks and is induced by specific physical or environmental stimuli (cold, heat, exercise, pressure, sunlight, vibration, water, etc.). According to the current international classification, it includes physical urticarias (dermographism, delayed-pressure urticaria, exercise-induced urticaria, cold urticaria, heat urticaria, solar urticaria, and vibratory urticaria) and non-physical urticarias caused by exposure to specific stimuli (cholinergic urticaria, contact urticaria, and aquagenic urticaria). In terms of frequency, more common types of CIndU are dermographism, cholinergic urticaria, and delayed-pressure urticaria. In clinical practice, it is often difficult to define the exact type of CIndU; management thus begins with accurate identification of a possible trigger and its avoidance. The definite diagnosis for CIndU requires obtaining a detailed medical history of a patient with comprehensive information about predisposing factors, physical examination, and provocation testing (challenge tests). It is always necessary to recognize the prophylactic options for all the types and to have access to different therapies (primarily second-generation H1 antihistamines, but also H2 antihistamines, hydroxyzine, doxepin, oral glucocorticoids, omalizumab/anti-IgE therapy, phototherapy, physical desensitization, immunomodulatory agents, etc.) individualized for each patient.