Cholinergic Urticaria
Cholinergic urticaria causes small, itchy bumps to appear on your skin when your body temperature rises and you start to sweat, triggered by activities like exercise, hot showers, stress, or even eating spicy foods.
Table of contents
- What is cholinergic urticaria?
- Identification codes
- Other names
- How common is it?
- Who gets cholinergic urticaria?
- What causes cholinergic urticaria?
- What triggers cholinergic urticaria?
- Risk factors
- Symptoms and characteristics
- Possible complications
- Types of cholinergic urticaria
- How is it diagnosed?
- Conditions with similar symptoms
- Treatment options
- Prevention strategies
- What to expect
What is cholinergic urticaria?
Cholinergic urticaria is a type of hives (raised red bumps on the skin, also called urticaria) that appears when your body temperature rises and you start to sweat. It is an immune reaction that happens when you are exposed to heat, like during exercise or taking a hot shower.[1]
The term “cholinergic” refers to acetylcholine, a chemical messenger released by your nervous system. When your body temperature increases, your nervous system releases this substance from nerve endings near the surface of your skin. In people with cholinergic urticaria, this chemical irritates the skin, causing an allergic reaction that brings on hives and swelling.[1]
Identification codes
L50.5
EB02.0
73098005
Other names
Heat bumps, Heat hives, Cholinergic angioedema urticaria
How common is it?
Cholinergic urticaria is 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, which are 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.[1]
Some studies suggest that cholinergic urticaria may affect approximately 5 to 7% of patients who have hives, and it accounts for about 10% of all young adults with urticaria.[3][9]
Who gets cholinergic urticaria?
Cholinergic urticaria can affect anyone. Symptoms often appear for the first time between the ages of 10 and 30 years.[1] While the disorder occurs in both sexes, it occurs more frequently in males.[5]
What causes cholinergic urticaria?
Experts still do not know exactly what causes cholinergic urticaria. One hypothesis centers around the cholinergic nervous system. When your body temperature rises, you start to sweat. In response, your nervous system releases cholinergic chemicals, specifically acetylcholine, from nerve endings near the surface of your skin. The acetylcholine irritates your skin, causing an allergic reaction that brings on hives and swelling.[1]
Multiple mechanisms may contribute to the development of cholinergic urticaria in a complex manner. These include the release of histamine (a substance that causes itching and inflammation), sweat allergy, cholinergic-related substances, blockage of sweat pores, and reduced sweating or absence of sweating.[2]
Some authorities suggest that rather than shifts in core body temperature alone, an allergy to a component of human sweat may be the immediate trigger. Studies have found that the sweat sensitivities in cholinergic urticaria and atopic dermatitis may be similar, and that sweat-induced histamine release from certain immune cells may be mediated by a specific antibody for sweat.[4]
What triggers cholinergic urticaria?
For nearly 9 in 10 people, exercise or physical exertion brings on cholinergic hives.[1] Any stimulus that causes your body to heat up and produce sweat can trigger this condition. Common triggers include:[1][5]
- Exercise and physical activity
- Hot showers, saunas, and hot tubs
- Hot weather or entering a hot room from a cooler place
- Spicy foods or hot beverages
- Emotional stress
- Anxiety or feeling angry or upset
- Fever
- Wearing an air- and water-tight bandage to protect a wound
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:[1]
- Allergic rhinitis (hay fever)
- Asthma
- Eczema
- Family history of cholinergic urticaria or chronic hives
- Hyperhidrosis (excessive sweating)
Symptoms and characteristics
Cholinergic urticaria typically presents with small papular hives all over the body that involve skin inflammation and sometimes severe discomfort. The symptoms appear and disappear rapidly and can occur on and off throughout the day without notice.[4]
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, though they can occur anywhere on the body. They almost never occur on the palms, soles, or underarms.[1][5]
The hives typically have these characteristics:[1][5][6]
- Small (1 to 4 millimeters across) raised bumps
- Round and raised appearance
- Red in color, often surrounded by a larger area of redness
- May join together to form larger welts that swell
- Itchy, burning, or tingling sensation
- Feel warm to the touch
- Usually last from about 15 to 90 minutes after stopping the activity that triggered them
Lesions generally first appear on the trunk and neck and spread outward to the limbs and face. Lesions are temporary, starting within minutes of the trigger stimulus and resolving within 90 minutes after stopping the initiating activity.[5]
Possible complications
Although rare, some people with cholinergic urticaria also develop additional symptoms:[1][5][6]
- Headaches
- Drooling or extra saliva in the mouth
- Fainting
- Heart palpitations or rapid heartbeat
- Shortness of breath or wheezing
- Bronchospasm (a tightening of the muscles in the airways)
- Upset stomach, indigestion, or diarrhea
- Abdominal cramps
- Low blood pressure
- Angioedema (swelling of the deeper layers of the skin)
In some rare instances, a person may develop anaphylaxis, a life-threatening allergic reaction that needs emergency medical attention. Very rarely, serious conditions such as hepatocellular injury or anaphylactic reactions have been reported.[5][6]
Types of cholinergic urticaria
Cholinergic urticaria can be divided into several subtypes based on the underlying mechanisms:[2][3]
Cholinergic urticaria with sweat hypersensitivity: This subtype refers to people who are hypersensitive to their own sweat. The hives are observed to coincide with perspiration points of sweating. In these cases, sweat-induced histamine release from certain immune cells may be mediated by a specific antibody for sweat.[4]
Cholinergic urticaria with reduced sweating: This subtype refers to people who have abnormally reduced sweating (hypohidrosis) or absence of sweating (anhidrosis). This can be acquired and generalized, associated with failure of the sweat control system, or localized showing sweat gland infiltration with certain immune cells.[3]
Cholinergic urticaria with pore blockage: In this subtype, the sweat pores become blocked, contributing to the development of hives.[3]
Idiopathic cholinergic urticaria: This refers to cases where the exact cause cannot be determined.[3]
How is it diagnosed?
If a healthcare provider thinks you have cholinergic hives, they will likely refer you to an allergist or dermatologist. They will examine your skin and ask questions about your symptoms.[1]
The presentation of typical lesions and symptoms in the context of a typical trigger is often sufficient evidence to form a clinical diagnosis, and no further testing is required. Asking the patient to exercise or take a hot bath can allow inspection of the induced lesions.[5]
They might also run tests, which could include:[1][3][5]
- Exercise tests using a treadmill, stationary bike, or other equipment to induce sweating. The most reliable way to reproduce cholinergic urticaria is to cause the patient to sweat from a stimulus such as during exercise.
- Methacholine injections to test your body’s sensitivity to cholinergic substances. Traditionally, an intradermal injection of methacholine has been used to produce a flare-up of cholinergic urticaria containing characteristic wheals. However, only about one-third of patients demonstrate a positive test, so the test cannot be used to exclude a diagnosis.
- Autologous sweat injection where the person’s own sweat is injected into the skin to check for sweat hypersensitivity.
Keeping a journal about when you get hives can help you narrow down whether certain things during your daily activities are triggers.[20]
Conditions with similar symptoms
Several other conditions should be considered when diagnosing cholinergic urticaria:[5]
- Acute urticaria
- Chronic urticaria
- Contact urticaria syndrome
- Urticarial vasculitis
- Dermographism urticaria
- Pressure urticaria
- Solar urticaria
Treatment options
The mainstay of treatment is identifying and avoiding triggers, if possible. Rapid cooling of the skin may abort an attack. Sometimes, an attack of cholinergic urticaria can be stopped by rapid cooling.[5][12]
First-line treatment: The primary pharmacological agents are oral second-generation antihistamines. These are recommended over older antihistamines because of their safer side effect profiles. They are usually taken daily, though as-needed regimens are possible if triggers are identifiable in advance. If needed to control symptoms, second-generation antihistamines can be increased to two to four times the normal dose, though a higher risk of side effects exists with higher doses.[5][15]
Additional medications: Other medications may be added to control symptoms, including:[12][14]
- First-generation antihistamines
- H2 antihistamines (medications that block a different type of histamine receptor)
- Leukotriene receptor antagonists
- Brief corticosteroid bursts for severe cases
A combination of H1 and H2 antihistamines has been found to be more effective based on complete control of cholinergic urticaria with a lower relapsing rate.[14]
Sweat therapy: Forced perspiration by excessive body warming through sauna, hot bath, or exercise used daily may reduce symptoms through exhaustion of inflammatory mediators.[4]
Advanced treatments: In cases that do not respond to standard treatments, other options include:[12]
- Beta-blockers such as propranolol
- Danazol (a synthetic androgen)
- Omalizumab (anti-antibody therapy)
- Cyclosporine (an immunosuppressive medication)
- Rapid desensitization with autologous sweat
Prevention strategies
Patients with cholinergic urticaria should try to avoid the precipitating factors when possible. These include exercise and any activity that causes sweating, such as elevated environmental temperature, hot food, sauna baths, immersion in hot water, emotional stress, and highly spiced foods.[12]
Practical prevention strategies include:[20]
- Stay cool and dry by avoiding prolonged periods in hot and humid environments
- Wear antiperspirant to reduce sweating
- Keep a soft cloth handy to dab off moisture when you start to sweat
- If spending time outdoors, avoid the hottest times of the day
- Drink plenty of fluids to stay hydrated and help regulate body temperature
- Learn and track your specific triggers by keeping a journal
Modifying your diet may be helpful because cholinergic urticaria attacks can sometimes result from hot foods and beverages, highly spiced foods, and alcohol.[12]
What to expect
Cholinergic urticaria may significantly impair quality of life, especially in relation to normal day-to-day activities. Many people find they need to avoid exercise and other activities to prevent urticaria, which can lead to avoiding sports and social activities.[4][13]
The good news is that more than one-half of patients with chronic urticaria will have resolution or improvement of symptoms within a year.[15] In evaluating any response to therapy, it is important to consider that cholinergic urticaria can clear spontaneously.[12]
The lesions typically resolve without treatment between a few minutes and an hour later. They usually have no lasting effects, and individual hives do not leave permanent marks, bruising, or scarring on the skin.[4][6]