What is Cholinergic Urticaria (Physical Heat Hives)? An Overview & Definition:
Cholinergic Urticaria is a medical term used to describe a subcategory of physical urticaria (hives). It is characterized by a hypersensitive response in the skin as a result of the body increasing in temperature, or the precipitating release of sweat. Individuals may experience a cholinergic urticaria reaction in response to any activity that increases overall body temperature (or causes a sweat release). This can be from passive heating of the body (ie, sitting in a warm room), or active heating (ie, exercise or physical activity). It can also be precipitated by a strong emotional reaction, excitation, etc. Some examples include:
- Taking a hot shower or bath
- Eating spicy foods
- Exercising or doing physical activities that increase body temperature
- Emotional response (sadness, anxiety, anger, laughter)
- Changing from a cool environment to a hotter environment without allowing the body time to slowly acclimate to the temperature difference (such as walking from a cold room to a hot room)
Individuals experiencing cholinergic urticaria are otherwise healthy and exhibit no symptoms unless they are forced to experience a heat stimulus (as mentioned above). At that point, they may have a hives response to the increase in temperature.
This condition gets its name from 2 sources:
- “Cholinergic” which means “related to acetylcholine.” Acetylcholine is a chemical used in the parasympathic nervous system. It acts as a neurotransmitter. Acetylecholine seems to be involved in cholinergic urticaria reactions. It appears that when acetylcholine is released at the nerve endings in the skin, this can initiate a hives response.
- “Urticaria” originates from the Latin word urtica, which means stinging nettle. A stinging nettle is the name of a plant that has small hair-like needles that sting if touched by humans. In urticaria, histamine is released which produces a very prickly and itchy feeling in the skin.
Cholinergic Urticaria is often referred to as “heat hives” or “heat urticaria.” Individuals often feel a burning, itchy and prickly feeling during an attack, which subsides once the individual is able to cool down or reduce body temperature.
This condition is not to be confused with similar conditions such as Miliaria Rubra (Prickly Heat), or Exercised Induced Anaphylaxis (swelling reaction in a response to exercise). Individuals with Miliaria Rubra feel similar symptoms, however, this condition is caused by bacterial infection/occlusion of sweat glands.
Exercised Induced Anaphylaxis is also similar in that a reaction occurs in response to heat. However, individuals with this condition usually develop a swelling reaction, which could lead to anaphylactic shock.
Cholinergic Urticaria Age, Sex, Race, Location, and Prevalence Factors:
- Age-- Cholinergic Urticaria can occur at almost any age. Individuals have experienced cholinergic urticaria symptoms in young children (as young as 3-6 years old), adolescents, and all through adult life. Most studies reveal that the majority of individuals develop the condition in the late teen years or early twenties. However, it can occur at any age, and may sometimes go through periods of remission and flare ups, or may go away altogether.
- Sex–Cholinergic Urticaria can occur in both men and women. Some research has indicated that it is more prevalent in men than women. However, many women do suffer with the condition.
- Race–Cholinergic Urticaria can occur in all races equally (African American, Caucasian, Asian, European, Hispanics, etc.).
- Location–Cholinergic Urticaria can occur in individuals in almost every major location. It affects people in all parts of the world.
- Population Prevalence–Cholinergic urticaria is a fairly common type of the physical hives. Studies vary & some suggest that between 2%-12% of all individuals suffering from chronic urticaria have the cholinergic urticaria subtype. In terms of the general population, some data suggests 0.2% may suffer with this condition. However, this number could vary as many individuals with this condition are misdiagnosed or do not seek medical treatment. Also, it appears to be a world-wide occurrence. People have reported this condition in various locations such as the United States, Canada, United Kingdom, etc.
Does Cholinergic Urticaria Appear Suddenly or Slowly?
Cholinergic urticaria often appears suddenly, with no prior symptoms, as an individuals body temperature rises. Many individuals with this condition report that they were fine one day, and the next day this condition suddenly appeared, and often persists for weeks, months, years, or even decades.
This condition can also disappear in the same manner. Individuals often find that they no longer experience the reaction, and the condition may no longer bother them.
In addition, individuals with cholinergic urticaria often go through periods of hypersensitivity, and then reduced sensitivity. Some individuals may only struggle with the condition in certain months or seasons (i.e., summer, winter).
Also, individuals may experience a hives reaction multiple times per day, in their sleep, and more. Any time a person with physical heat hives becomes heated, they are at risk for a hives reaction.
Some individuals may feel better after the hives appear, and may not be as sensitive to temperature increases for the rest of the day. This is sometimes due to the release of histamine having a refractory period. Not all individuals experience this relief, and many have reported multiple severe attacks within 1 day.
Cholinergic Urticaria’s Effect on Quality of Life
Individuals with cholinergic urticaria often have a varying degree of symptoms. Some may have severe reactions to heat, while others have a greater tolerance and less painful reactions.
For those with severe cholinergic urticaria symptoms, it may lead to a reduction in the quality of life. Individuals may have to alter their lifestyle in some ways to avoid hives reactions. Some of these changes may include:
- Wearing lighter clothing
- Changing jobs or finding work in a cool and stress-free environment
- Avoiding potentially stressful situations
- Altering diet to avoid spicy foods (which may evoke a reaction)
- Avoiding hot buildings, rooms, or outdoor weather during warm months
- Taking cooler showers
In addition, individuals may also experience periods of sadness (or depression) and/or frustration due to the condition. They also may feel embarrassed when having a hives reaction in public.
How is Cholinergic Urticaria (chronic heat hives) Diagnosed?
Cholinergic urticaria can be diagnosed by a physician or any licensed medically trained person specializing in hives or skin conditions. A diagnosis could be as simple as the doctor listening to your symptoms, or they may give a few simple observation-based tests to observe the reaction before confirming the diagnosis.
One test that is sometimes given is called an “exercise or sweat test.” In this test procedure, doctors may observe your symptoms before exercising or becoming hot. Then, you will be placed in an environment in which you will exercise or be placed in a room that is heated. They will then observe your symptoms during the hives reaction & make the diagnosis based on your physical symptoms.
Another test that is sometimes performed (usually just for research purposes) involves injecting acetylcholine into the body. In some cases it can cause a wheal (small allergic response). However, not everyone with cholinergic urticaria will show a reaction to this specific test procedure.
Other than these simple tests, there is currently no other way to diagnose cholinergic urticaria. In fact, the condition can sometimes be misdiagnosed, and many individuals will not get a proper diagnosis right away.