Urticaria is a condition characterized by itchy hives or wheals. It can be acute or chronic. Chronic spontaneous urticaria (CSU) is the most common form of chronic  urticaria with about 80% of cases being spontaneous, where no specific trigger factor is found. The duration of CSU is often on average 2 years. In some cases, a harmless parasite infection can be involved. In addition, in some forms of urticaria, the rash is triggered by a physical stimulus, such as cold, heat, exercise, pressure, etc. The therapy consists in avoidance of the trigger, or in a treatment with oral antihistamines for CSU. In refractory form, a treatment with omalizumab (xolair®) can be very successful.