Dermatology Made Easy is based on the most popular topics from DermNet NZ's vast array of material. The book combines the essential focus of the ‘Made Easy’ book series with the authority and knowledge base of DermNet NZ's unparalleled resources.
Author: Vanessa Ngan, Staff Writer, 2006.
Cholinergic urticaria is a common physical urticaria that is caused by sweating. It is sometimes referred to as heat bumps, as the rash appears as very small (1-4mm) weals surrounded by bright red flares.
A rise in core body temperature resulting in sweating causes the rash in cholinergic urticaria. Common triggers include:
The rash appears rapidly, usually within a few minutes of sweating, and can last from 30 minutes to an hour or more before fading away. The mean duration is around 80 minutes. Typical signs and symptoms of the rash include:
People who are more likely to suffer from cholinergic urticaria include:
It occurs in both men and women, but appears to be more common in men than women. The condition tends to first appear in people aged between 10 and 30 years and persists for a number of years before it becomes less severe or goes away altogether. The natural course of cholinergic urticaria is quite variable, with most patients experiencing slow resolution over several years.
Once the cause of the rash is identified, it may be possible to avoid situations that trigger it. However, in many cases it is difficult to stop sweating, particularly in warm climates and if exercising is part of a daily routine. Sometimes rapid cooling can prevent an attack. For most patients regular administration of an oral antihistamine such as cetirizine can be helpful in preventing the condition from arising. Beta-blockers such as propranolol have also been reported to be useful.
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