Is heat or cold better for hives
Cholinergic Urticaria: Can Heat Cause Hives?
Hives are a skin reaction of itchy bumps that may burn or sting. They can develop not only from an immune response to an allergen but also to heat.
While you may think of hives or urticaria as resulting from an allergic reaction, they can also be caused by heat. These are called heat hives or cholinergic urticaria.
In some people, a rise in temperature can produce the chemical histamine, similar to what happens when your immune system fights allergies. Histamine dilates blood vessels and results in swelling.
There is limited research on cholinergic urticaria. The few available studies estimate a wide prevalence range of
If you notice hives tend to break out when your body temperature rises, it may be a sign that heat triggers your hives. Any exposure to heat could potentially trigger heat hives. This can include:
- bathing in warm or hot water
- being near a heat source like a stove
- being outdoors in the sun
- eating hot food
According to research from 2022, physical factors that can contribute to the development of heat hives include:
- being allergic to sweat
- clogged sweat ducts, lack of sweating
- medications or substances that affect the neurotransmitter acetylcholine
Although being allergic to sweat is rare, research shows that 66% of patients who get heat hives also have a histamine response against antigens in their sweat.
In rare cases, heat hives
Get step-by-step instructions on how to use an EpiPen.
Heat rash vs. hives
Heat hives share similar causes and symptoms with many forms of heat rash, also known as miliaria.
Heat rash can also be
While heat rash tends to fade on its own, consider visiting your doctor for more severe or persistent cases. Your doctor can provide a proper diagnosis and help you determine whether youre experiencing hives or heat rash.
The symptoms of heat hives are similar to hives caused by other triggers such as insect bites, allergies, or medications.
Hives can appear as red, itchy welts ranging in size from less than half an inch up to several inches in diameter. Hives on darker skin tones may appear closer to the color of the skin.
Most cases of hives caused by heat appear within a few minutes after exposure and will subside within 1-2 hours. However, heat hives can also be accompanied by angioedema, which is swelling beneath the affected skin caused by leaking blood vessels.
In some cases, you can also experience other symptoms along with heat hives. These include:
- fatigue or weakness.
- faintness
- nausea
- diarrhea
- headache
You may be experiencing exercise-induced anaphylaxis if you also have the following symptoms:
- difficulty breathing
- wheezing
- abdominal pain
- nausea
- headache
Call 911 if you experience these symptoms. If you have an EpiPen, you should administer the medication while you wait for help to arrive.
If your symptoms arent severe but interfere with your lifestyle, see your doctor. A simple evaluation and conversation about your symptoms may be enough for them to diagnose heat hives.
Sometimes, your doctor may want to conduct tests to gather more information about the condition. These may include:
- A passive warming test: This will raise your body temperature with warm water or an increased room temperature. Your doctor can observe your bodys reaction when exposed to increased heat.
- A methacholine skin challenge test: Your doctor may inject a medication called methacholine into your body and observe for a reaction. However, not everyone with heat hives gets a positive result, so the doctor may use this test in combination with others.
- An exercise challenge test: Your doctor will have you exercise and watch for symptoms of CU. You may also be measured with other medical instruments during the test.
You should see a doctor immediately if you suspect you have exercise-induced anaphylaxis, which must be attended to as soon as symptoms occur.
Many cases of heat hives fade on their own in a few hours, but certain home remedies, prescription medications, and prevention techniques can ease symptoms and alleviate flare-ups.
Natural remedies
Home remedies you can try include aloe vera, which has known anti-itching properties, or a colloidal oatmeal bath, which
But prior to topical applications of this sort, remember to check the ingredients to ensure that you arent allergic to any of them.
You can also take a few precautions to help prevent heat hives:
- Try to keep cool while exercising.
- Prevent exposure to areas of high humidity.
- Avoid prolonged periods of direct sunlight exposure.
Medications
If such home remedies dont work, your doctor may recommend beginning taking an antihistamine such as:
- H1 antihistamines such as citirizine (Zyrtec, Aller-Tec, and Alleroff) or loratadine (Claritin)
- H2 antihistamines (H2 blockers or antagonists) such as famotidine (Pepcid, Pepcid AC) or cimetidine (Tagamet, Tagamet HB)
If these medications dont relieve the symptoms sufficiently, your doctor
In some cases, your doctor may prescribe a medication off-label. One example of such medication is dupilumab (Dupixent), which is another biologic medication that
Most instances of heat hives can be treated at home and eventually fade on their own. However, you should seek immediate medical attention if swelling occurs in your throat that makes it difficult to breathe. This can be a sign of a serious allergic reaction and anaphylaxis.
You and your doctor can work to identify the specific triggers of your heat hives and develop a prevention plan with ways to ease symptoms if flare-ups do occur.
Hives
About hives
Hives (urticaria) are common skin rashes characterised by one or many wheals (lumps) of reddened, raised and itching skin. The wheals can vary in size, from relatively small to as large as a dinner plate. The wheals may be circular, oval or annular (ring-shaped).
Hives can affect any part of the body, but is common on the torso, throat, arms and legs. The wheals generally appear in clusters, with one cluster getting worse as another gets better. Most wheals disappear without a trace within a few hours, only to be replaced by a new one elsewhere on the skin. Wheals that persist in exactly the same spot for more than 24 hours may indicate a different disorder known as urticarial vasculitis. In acute (short-lived) hives, the wheals may come and go for a few days or weeks. In rare cases of chronic hives, wheals may persist for more than 6 weeks. The wheals come and go for months or even years. It is thought that around one in every 6 people will experience an attack of acute hives at some point in their lives. In most people this is not due to allergy.
Mast cells and histamines
Underneath the lining of the skin, gut, lungs, nose and eyes are mast cells. These are designed to kill worms and parasites.
Mast cells contain chemicals including histamine. When these are released into the skin in small amounts, they cause itching and irritation. When large amounts are released into the skin, fluid leaks out of blood vessels, resulting in swelling of the skin (hives).
Occasionally, hives produce swelling without an itch.
Symptoms of hives
Symptoms of hives include:
- raised circular wheals that look like mosquito bites these are red on the outer rim and white in the centre, and each wheal lasts for around 2 to 4 hours (rarely up to 24 hours). Wheals appear in batches or clusters, and as one batch fades away a new batch appears
- localised itching
- with acute urticaria, the rash may last for days or weeks
- with chronic hives, the rash may persist for months to years, occasionally decades.
Causes of hives
In 80% of cases the cause of hives is unknown. Some factors known to cause hives include:
In chronic hives, it is rare to find a cause, although aspirin and codeine may aggravate it.
Treatment for hives
If a trigger is identified and it is possible to avoid that trigger, then the hives will resolve. Where no trigger is found, or the trigger cannot be avoided, treatment may include:
- avoidance of factors that make the condition worse such as aspirin, codeine, sunshine, heat and hot showers
- antihistamines some people require 2, 3 or even 4 tablets a day to control hives. These are available from pharmacies without prescription. Some antihistamines cause drowsiness.
For chronic hives, there are a number of other medications that can be prescribed.
Where to get help
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Key facts
- Hives, also known as 'urticaria' or 'nettle rash', is a skin rash that can occur for a range of reasons, including allergies, medicines or infections.
- A hive rash looks like red or skin-coloured raised bumps or welts on the skin, which are usually itchy.
- A hives rash is caused when the body produces a substance called histamine, which is released by the body in response to a perceived threat.
- Hives is diagnosed clinically, meaning that your doctor can diagnose the rash by talking to you and looking at your rash.
- The rash usually resolves on its own, but if a hives rash continues or get worse, antihistamines can help relieve the symptoms.
What is hives?
Hives is also known as 'urticaria' or 'nettle rash'. This skin rash can have a range of triggers, most commonly an allergic reaction. Other triggers include medicines or infections. Sometimes the trigger is unknown.
What are the symptoms of hives?
The hives rash looks like raised bumps or welts on the skin that are usually itchy, but may also sting. These can be red or skin-coloured. The raised areas of skin are known as wheals.
Patches of hives often join together to form larger swollen patches or urticaria. The affected area of skin can vary in size from quite small to about as large as a dinner plate. The patches of hives often join together to look like larger swollen patches of urticaria.
The hives rash can last for a few minutes to hours, and usually disappears within 24 hours. In rare cases, the rash can last for weeks.
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What causes hives?
A hives rash is caused when your body produces a substance called histamine. This is a protein released by the body in response to a perceived threat (trigger).
In most cases, it is not known what triggers this reaction. Sometimes, urticaria can occur in response to:
Other triggers may include:
- cold air or water
- heat or sunlight
- vibration
- scratching
- sweating
- certain foods and drinks, such as spicy food, alcohol or coffee
In children, hives can be caused by a viral infection. This is why they sometimes go together with a cold or diarrhoea.
Hives that lasts for days at a time are almost never due to an allergy, apart from some cases of medicine allergy.
Stress rarely causes hives, but stress can make the symptoms worse.
When should I see my doctor?
You should see you doctor if you have a rash that looks like hives.
Some people have hives that don't go away or recur on a frequent basis. This is known as chronic urticaria. See your doctor if you have hives that keep coming back.
If you have taken antihistamines for your hives but they do not control the symptoms, discuss alternative treatment options with your doctor.
If your baby gets hives repeatedly, it's important to see your doctor. This could indicate an allergy to something they are frequently fed, such as cow's milk.
Sometimes hives can last for a long time. If you have hives for more than 6 weeks, your doctor may refer you for more tests to check if an underlying infection or chronic immune disorder is causing the symptoms.
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How are hives diagnosed?
Hives is diagnosed clinically. Your doctor can diagnose the rash by talking to you and looking at your rash.
How are hives treated?
Hives usually resolve on its own without treatment. However, if the hives rash continues or gets worse, it can be treated with antihistamines. You can buy antihistamines over the counter at pharmacies.
Ask your pharmacist for advice on which antihistamine to take, as some will cause drowsiness, and can be taken at bed time if your rash is itchy and keeping you awake at night. Other antihistamines are not likely to cause drowsiness, so you can take them before driving or going to work or school.
To search medicines by active ingredient or brand name, use the healthdirect Medicines search feature.
Can hives be prevented?
If your hives are caused by a specific trigger, such as a food or medicine, you should avoid your known triggers.
Since most people don't know what caused their hives, it can be difficult to prevent.
Resources and support
For more information about the causes and management of hives see the Australasian Society of Clinical Immunology and Allergy website.
The Royal Children's Hospital has a fact sheet on hives for parents to learn about care at home and more severe reactions.
You can also call healthdirect on 1800 022 222 at any time to speak to a registered nurse (known as NURSE-ON-CALL in Victoria) for more information and advice.
