Triggers and causes

Chronic urticaria can:

• last for years (and sometimes decades)
• sometimes be initially caused by a serious underlying disease
• frequently impair quality of life to the point where patients cannot function without medicine to suppress itchiness.

Serious cases of chronic urticaria therefore require a thorough and systematic search for the triggers and causes, with the goal of identifying and removing them.

Urticaria can be generated by many different causes and triggers because mast cells can be activated through a wide variety of factors. Chronic hives are therefore categorised into subgroups based on those mechanisms and the frequency of their occurrence. More than two-thirds of all urticaria cases can be attributed to one of the following groups:

• autoreactive urticaria: intolerance to the body's own substances
• infectious urticaria: reaction to chronic centres of infection or inflammation that potentially do not cause any symptoms beyond the urticaria, such as in the digestive tract
• intolerance-related urticaria: hyper-sensitivity to food additives (e.g. colour, aroma or preservatives), histamine or drugs
• other rare causes of chronic urticaria, such as food allergies