Spontaneous urticaria is the most common form of urticaria. One in four people develop spontaneous urticaria in the course of their lives. The key characteristic is that the symptoms occur “out of the blue”. As a rule, the signs of illness (wheals, itchiness and angioedema) cannot be reproduced on command and triggers and causes responsible cannot be determined upon first sight. Generally spontaneous urticaria lasts only a few days or weeks. It is then defined as acute spontaneous urticaria. For up to 10 % of all patients with spontaneous urticaria, the symptoms last longer than 6 wheals. This is then called a chronic spontaneous urticaria.