What is cholinergic urticaria?
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.
What causes cholinergic urticaria?
A rise in core body temperature resulting in sweating causes the rash in cholinergic urticaria. Common triggers include:
- Hot baths/showers
- Occlusive dressings
- Eating spicy foods
- Emotional stress
What are the clinical features of cholinergic urticaria?
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:
- Itching, burning, tingling, warm sensation preceding the onset of numerous small weals with surrounding bright red flares
- Rash is often very itchy
- Rash may appear anywhere on the body but is more prominent on the upper trunk and arms. It does not affect the palms or soles and rarely the armpits.
- Sometimes the tiny weals join together to form a large swelling
- Patients who are more severely affected may experience systemic symptoms such as headaches, salivation, palpitations, fainting, shortness of breath, wheezing, abdominal cramps and diarrhoea
- Rarely, patients with cholinergic urticaria can have more severe reactions such as anaphylaxis so should probably not exercise alone.
Who gets cholinergic urticaria?
People who are more likely to suffer from cholinergic urticaria include:
- Those who already suffer from generalised chronic urticaria
- People with allergic type conditions, e.g. asthma, rhinitis, atopic dermatitis (eczema).
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.
What is the treatment for cholinergic urticaria?
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.