Cholinergic Urticaria

What is cholinergic urticaria?

Cholinergic urticaria are hives (raised red bumps on your skin) that appear when your body temperature rises and you start to sweat. It’s an immune reaction that happens when you’re exposed to heat, like exercise or taking a hot shower. Other names for cholinergic urticaria include heat bumps or heat hives.

Cholinergic urticaria can affect anyone. Symptoms often surface for the first time between the ages of 10 and 30.

The term “cholinergic” refers to a neurotransmitter (chemical messenger) called acetylcholine (Ach). Your parasympathetic nervous system releases it. “Urticaria” is the medical term for hives.

Is cholinergic urticaria rare?

No, it’s actually quite common. As many as 1 in 5 people have hives at some point in their lives. Cholinergic urticaria accounts for about 1 in 3 cases of physical hives (hives that have a physical cause, like exposure to heat, cold or pressure.) About 7% of people with chronic hives (hives that last longer than six weeks) have cholinergic urticaria.

What causes cholinergic urticaria?

Experts still don’t know exactly what causes cholinergic urticaria. One hypothesis centers around the cholinergic nervous system as the culprit. Here’s how it works:

1. When your body temperature rises, you start to sweat.
2. In response, your nervous system releases cholinergic chemicals (acetylcholine) from nerve endings near the surface of your skin.
3. The acetylcholine irritates your skin, causing an allergic reaction that brings on hives and swelling.

Cholinergic urticaria risk factors

A risk factor is something that increases your chances of developing a certain condition. You may be more likely to develop cholinergic urticaria if you have chronic hives. Other risk factors include:

• Allergic rhinitis (hay fever).
• Asthma.
• Eczema.
• Family history of cholinergic urticaria or chronic hives.
• Hyperhidrosis (excessive sweating).

What triggers cholinergic urticaria?

For nearly 9 in 10 people, exercise or physical exertion brings on cholinergic hives. Other triggers include:

• Anxiety.
• Feeling angry or upset.
• Entering a hot room (or the hot outdoors) from a cooler place.
• Fever.
• Hot weather.
• Hot showers, saunas and hot tubs.
• Spicy foods.
• Stress.
• Wearing an air- and water-tight bandage to protect a wound.

What are the symptoms of cholinergic urticaria?

Heat bumps typically appear a few minutes after you start sweating and may last for 20 to 30 minutes. For some people, the hives linger for more than an hour. These hives tend to appear on your arms, face and upper trunk.

The hives may look like small red dots (pinpoints) overlying a background of redness (erythema), or they may join together to form larger welts that swell.

What does cholinergic urticaria feel like?

People with cholinergic urticaria may develop hives that:

• Itch.
• Burn.
• Tingle.
• Feel warm to the touch.

What other symptoms occur along with cholinergic urticaria?

Although rare, some people with cholinergic urticaria also develop:

• Drooling.
• Fainting (syncope).
• Headaches.
• Heart palpitations.
• Shortness of breath (dyspnea).
• Upset stomach (indigestion) or diarrhea.
• Wheezing.

How is cholinergic urticaria diagnosed?

If a healthcare provider thinks you have cholinergic hives, they’ll likely refer you to an allergist or dermatologist. They’ll examine your skin and ask questions about your symptoms.

They might also run tests, which could include:

• Exercise tests using a treadmill, stationary bike or other equipment to induce sweating.
• Methacholine injections to test your body’s sensitivity to cholinergic chemicals.
• Passive warming tests using heated bath water or a heated room to raise your body temperature. 

How do you get rid of cholinergic urticaria?

The frequency and severity of cholinergic urticaria often improve as you age. The hives may resolve in a few years. In the meantime, your healthcare provider may recommend these cholinergic urticaria treatments to ease your symptoms:

• Antihistamines.
• Asthma medications.
• Blood pressure medications.
• Sweat-reducing drugs (anticholinergics).

What are the complications of cholinergic urticaria?

In rare instances, cholinergic urticaria occurs along with exercise-induced anaphylaxis. Anaphylaxis is a potentially life-threatening allergic reaction that can swell your airways, making it difficult to breathe. If this happens to you or someone you know, call 911 and seek immediate medical care. It’s also a good idea to carry an epinephrine injector (EpiPen®) if you know you’re prone to anaphylactic attacks.

Can you prevent cholinergic urticaria?

You can’t totally prevent cholinergic urticaria because you can’t keep yourself from sweating or getting warm. It’s a natural function that cools your body and helps regulate your temperature. And you shouldn’t skip physical activity, as physical activity helps keep you healthy.

But there are steps you can take to reduce your risk of heat hives:

• Avoid spicy foods.
• Exercise in the early morning or late evenings when outside temperatures are lower.
• Find healthy ways to cope with stress and manage anxiety.
• Take warm (not hot) showers or baths.
• Wear lightweight, loose-fitting, sweat-wicking clothing.

How long does cholinergic urticaria last?

Cholinergic urticaria typically improves and goes away over time. For almost 15% of people with the condition, the symptoms resolve completely.

When should I call my healthcare provider?

Call your healthcare provider if you develop:

• Bumps that look infected (pus-filled or painful to touch).
• Hives and swelling.
• Unexplained skin rash.
• Severe itching.
• Shortness of breath or difficulty breathing.
• Signs of anaphylaxis (call 911).

What should I ask my provider?

You may want to ask your healthcare provider:

• What caused the cholinergic urticaria?
• How can I reduce my risk of heat hives?
• What’s the best cholinergic urticaria treatment for me?

What’s the difference between heat bumps (cholinergic urticaria) and a heat rash?

Heat rash (also called prickly heat or miliaria) is a type of heat illness. You develop this skin rash in response to heat and humidity. It occurs when sweating doesn’t effectively lower your body temperature to cool you down. A heat rash can be a warning sign of a more serious heat illness like heat exhaustion or heatstroke.