Cholinergic urticaria (heat bumps) can occur when a person’s core body temperature rises. Possible causes include exercise, stress, weather, and eating spicy foods. Small, round, itchy papules appear that usually fade within an hour.
The lesions typically resolve without treatment between
The word “cholinergic” refers to a part of the nervous system that controls muscle contraction, blood vessel dilation, and slowing of the heart rate.
In this article, we look at the signs and symptoms of cholinergic urticaria, why it happens, and how to treat or prevent it.
Cholinergic urticaria tends to appear soon after a person’s body heats up. It can occur anywhere but is more likely to affect the trunk or arms.
The lesions that occur with cholinergic urticaria usually:
1–5 millimeters (mm)across
- are small and numerous
- are round and raised
- are the same color as the person’s skin
- are itchy
- last from a
few minutes to one hour
The rash may include any combination of the following features:
- itching or tingling at the onset of the rash
- burning or itching in areas affected by the rash
- areas of small wheals or raised bumps on the skin
- larger wheals that lead to more significant areas of swelling
- angioedema, or swelling of the deeper layers of the skin
In rare cases, heat bumps may be linked to other problems throughout the body, such as:
- heart palpitations
- abdominal cramps
- low blood pressure
- bronchospasm, a tightening of the muscles in the airways
- wheezing or shortness of breath
In some instances, a person may develop anaphylaxis, a life threatening allergic reaction that needs emergency medical attention.
Anaphylaxis: Symptoms and what to do
Anaphylaxis is a severe allergic reaction that can be life threatening. The symptoms develop suddenly and include:
- swelling of the face or mouth
- fast, shallow breathing
- a fast heart rate
- clammy skin
- anxiety or confusion
- blue or white lips
- fainting or loss of consciousness
If someone has these symptoms:
- Check whether they are carrying an epinephrine pen. If they are, follow the instructions on the side of the pen to use it.
- Dial 911 or the number of the nearest emergency department.
- Lay the person down from a standing position. If they have vomited, turn them onto their side.
- Stay with them until the emergency services arrive.
Some people may need more than one epinephrine injection. If the symptoms do not improve in 5–15 minutes, or they come back, use a second pen if the person has one.
Cholinergic urticaria can result from any activity that causes excessive sweating.
- hot baths
- sitting in a sauna or hot tub
- being in a warm room
- exposure to hot temperatures, such as hot weather
- having a fever
- being angry or upset
- eating spicy food
- consuming alcohol, in
The body tends to release in response to an allergic reaction.
To diagnose cholinergic urticaria, a doctor will likely consider the symptoms and ask the person what they were doing when they started.
In some cases, they may ask a person to take a warm bath or do some exercise to see how urticaria appears.
A doctor can inject a drug called methacholine into a person’s skin to see if cholinergic urticaria develops. However, they are unlikely to use this test as it cannot reliably diagnose or rule out cholinergic urticaria.
Treatment and management options vary between individuals.
- medications, such as:
- lifestyle changes to avoid triggers, such as:
- avoiding places and activities that warm the body
- cutting out spicy foods
- limiting alcohol consumption
- stress management techniques, if stress appears to contribute
- ultraviolet (UV) phototherapy
While treatment may help, it may not completely prevent cholinergic urticaria.
Some dietary choices may help reduce the risk of overheating the body’s core and therefore of developing cholinergic urticaria.
It may help to avoid:
- hot drinks
- spicy foods
- alcoholic drinks
Cholinergic urticaria often starts between the ages of 10 and 30 years and gradually stops happening over time.
Here are some questions people often ask about cholinergic urticaria.
How do you get rid of cholinergic urticaria?
The rash will fade after a person stops the activity that caused the reaction. Avoiding situations that lead to overheating and sweating can prevent it. This is not always possible, however, and doctors can prescribe medication to resolve or prevent a rash.
Should I worry about cholinergic urticaria?
In most cases, cholinergic urticaria goes away when the person stops the activity that caused it and does not have any serious effects. In some cases, however, a person may develop a more severe reaction. If the rash occurs with other symptoms, the individual should ask a doctor for advice. Severe swelling and breathing difficulty may be signs of anaphylaxis, a life threatening reaction that needs immediate medical attention.
What does cholinergic urticaria feel like?
A rash of small bumps can appear on the skin. They may be itchy, prickly, or burning. Sometimes, larger bumps or wheals may develop with more severe swelling.
How long does cholinergic urticaria last?
It usually passes within a few minutes to an hour. According to DermNet NZ, wheals usually last 15–30 minutes, and the overall rash should disappear 90 minutes after starting the activity that triggered it.
Cholinergic urticaria is a type of hives or skin reaction that occurs when the body temperature rises. Experts do not know precisely how it happens, but the sweating process may play a role.
People who experience frequent or long lasting symptoms may wish to speak to their doctor about ways to manage the condition.
If a person experiences other symptoms, such as breathing difficulty, they should seek immediate medical attention.