What Is Heat Rash
Share on Pinterest Skin products may clog the pores and lead to prickly heat.
Image credit: Sentient Planet, 2011
Prickly heat: What you need to know
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Miliaria rubra, commonly called prickly heat or heat rash, is a rash that causes the skin to turn red, along with a warm, stinging, or prickly sensation. The feeling is usually accompanied by small red dots in the affected area. The rash may also have small, raised bumps and blisters.
Prickly heat is often caused by exposure to warm temperatures and will normally clear up on its own after a few days. There are a few simple treatments to help reduce symptoms, but a visit to the doctor may be necessary in some situations.
The face, neck, shoulders, and chest are the most common places for prickly heat to occur, although it may show up anywhere. It can affect anyone, but children are more likely to have it than adults.
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Prickly heat is usually easy to identify due to its straightforward symptoms. Tiny red bumps and itching on an area of skin that has been exposed to heat and sweat for a long time are common signs of prickly heat.
Sometimes the red bumps can develop into a series of tiny blisters. The bumps or blisters may swell, become irritated or itchy, and redden as the rash progresses.
Prickly heat may spread on the body, but it is not infectious. Under normal conditions, there is no way to pass the rash on to other people.
Prickly heat is caused by trapped sweat. When the body is hot, it activates the sweat glands to create sweat on the skin. The sweat then cools the skin as it evaporates.
When the body is kept in this warm state, the constant sweat production can overload the sweat glands. This can cause the sweat ducts to become clogged, trapping sweat in the deep layers of the skin. This trapped sweat irritates the skin, which responds by producing a rash.
The most common trigger for prickly heat is exposure to heat for a long time. This may be especially true in very humid areas where the sweat has a harder time evaporating off the skin.
Prickly heat is common in people from cooler climates who travel to warmer climates. But it may also happen to a person in their usual climate when they experience more heat and sweat than normal.
Certain medications can also trigger prickly heat. Any drugs that raise the body temperature or alter the function of the sweat glands can increase the risk of prickly heat.
Some medications for Parkinson’s disease block the sweat, and tranquilizers and diuretics can change the fluid balance in the body, which can trigger symptoms of prickly heat as well.
A study in JAMA Dermatology noted that prickly heat developed where the bacteria Staphylococcus were found. These bacteria are normal, but the biofilm they produce can block sweat ducts and contribute to skin conditions. This would suggest that people with Staphylococcus on their skin may be more prone to prickly heat than others.
Share on Pinterest Cooling off to avoid additional sweat is recommended to treat prickly heat.
Prickly heat will usually go away on its own, but it may have bothersome symptoms. Many people can benefit from using home remedies. Products available over the counter or online, such as calamine lotion or topical steroid creams, can help treat the symptoms of redness, irritation, and swelling.
Treating prickly heat also involves cooling off quickly to avoid additional sweat. Sitting in front of a fan or in an air-conditioned room can help. Cold showers or baths can reduce body temperature and help prickly heat clear up faster.
Camphor and menthol may also have a cooling effect on the skin and help reduce the itchiness. In some cases, antihistamine medications can help reduce itching.
People who are prone to prickly heat may find relief from regularly washing the body with mild soap after sweating. This can reduce the amount of sweat and the number of bacteria on the skin.
Prickly heat can occur in people of all ages, is more common in children and infants. The developing sweat glands in a small child are less resilient and may be more likely to become clogged. Also, a child’s body is not used to adjusting to rapidly changing temperatures.
Children and infants are likely to experience prickly heat on their groin, neck, and face. The rash may be irritating and uncomfortable, but it will usually go away on its own. A cool bath can provide a child or baby with some relief from symptoms.
Parents and caregivers should avoid using oil-based skin products on children and infants to reduce the risk of clogging their sweat glands.
Share on Pinterest Skin products may clog the pores and lead to prickly heat.
Image credit: Sentient Planet, 2011
Preventing sweat from becoming trapped in the skin is an important step to avoid a rash. This may be as simple as not using certain skin products. Skin products that contain heavy oils or petroleum jelly may clog the pores and sweat glands, which could contribute to prickly heat.
Loose fitting clothing made of natural fibers, such as linen, cotton, and hemp, may reduce the amount of sweat that gets trapped on the skin.
Removing sweaty clothes after a long day of warm weather can prevent the sweat from getting trapped in the skin. Taking a shower to wash off the sweat and changing into clean clothes can prevent many cases of heat rash.
Avoiding a long time in hot and humid environments may help prevent symptoms, as well as using fans and air conditioners when possible. Regular cool showers or baths can reduce the body’s temperature and prevent excessive sweating.
Prickly heat powder can reduce symptoms. It is available from drugstores or to purchase online.
Prickly heat is a common condition that will usually resolve without medical treatment. Taking steps to prevent heat rash is the best way to avoid this annoyance.
If prickly heat starts to show, it may help to take a few quick steps to lower the body’s temperature and prevent additional sweating. Watching for any additional signs of heat stroke or exhaustion can help prevent a more serious issue.
If the symptoms of prickly heat persist or the rash seems to become infected, a person should seek medical attention. They may be referred to a dermatologist if there are signs of an underlying condition.
Last medically reviewed on October 4, 2017
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Medical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. We avoid using tertiary references. We link primary sources — including studies, scientific references, and statistics — within each article and also list them in the resources section at the bottom of our articles. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.
- Allen, H. B., Vaze, N. D., Choi, C., Hailu, T., Tulbert, B. H., Cusack, C. A., … Joshi, S. G. (2014, March). The presence and impact of biofilm-producing Staphylococci in atopic dermatitis. JAMA Dermatology, 150(3), 260-265
http://jamanetwork.com/journals/jamadermatology/fullarticle/1813229 - Backer, H. D., & Shlim, D. R. (2017, May 31). Problems with heat & cold
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https://www.cdc.gov/niosh/topics/heatstress/default.html - Santelli, J., Sullivan, J. M., Czarnik, A., & Bedolla, J. (2014, August). Heat illness in the emergency department: Keeping your cool [Abstract]. Emergency Medicine Practice, 16(8), 1-21
http://europepmc.org/abstract/med/25422847
What Is Heat Rash?
A heat rash is a common rash on the skin that can show up when you’re hot or you sweat a lot. It can make parts of your skin feel prickly or sting due to overheating. It can itch a lot, but it’s not dangerous.
Some people call a heat rash “prickly heat.” Doctors call it miliaria crystallina or miliaria rubra.
Anyone can get a heat rash, but it’s more common in babies and young children. Active people, newborns in incubators, and people on bed rest with fever also are more likely to get it.
What Causes a Heat Rash?
Heat rashes happen most often in humid, hot weather.
When you sweat too much, the ducts from the sweat glands in your skin become blocked.
This causes your sweat to leak into surrounding tissue, which leads to irritation and redness. You may feel the prickly sensation that gives this condition its name.
What Does a Heat Rash Look Like?
It looks like tiny bumps surrounded by red skin. It usually happens on clothed parts of your body, like your:
A heat rash usually gets better once your skin cools off. Most people don’t need to see their doctor about it.
But you should call your doctor if you or your child gets a heat rash with a fever, or if you think your skin is infected. Infected skin might:
- Feel painful or warm
- Look swollen or red
- Leak pus or form scabs
How Long Does a Heat Rash Last?
It usually lasts about 2 to 3 days. Call your doctor if it doesn’t go away after 3 or 4 days or if it seems to be getting worse.
Can a Heat Rash Spread?
Yes, it’s possible for a heat rash to spread to other parts of your body. That happens due to clogged sweat pathways.
Rashes are more likely to spread on parts of your body where your clothes are tight against your skin. That’s extra true when you sweat.
You don’t have to worry about spreading a heat rash to other people, though. It’s not contagious.
Is There a Heat Rash Treatment?
There’s no standard treatment to get rid of a heat rash. It usually gets better once your skin cools off.
You can do some things at home to get relief:
- Move to a cooler, less humid place.
- Take a cool shower or bath.
- Wear fewer layers of clothes, and loosen your clothes.
- Resist the urge to scratch your skin, or it could become infected.
- Keep your affected skin dry.
- Try calamine lotion, 1% hydrocortisone cream (not hydrocortisone ointment), or a prescription cream to ease your itching.
Don’t use ointments or creams that keep your skin moist. Also skip products that could clog your pores. Avoid using things like:
- Baby powders
- Ointments
- Scented lotions
- Lotions with petroleum or mineral oils
How Can You Prevent Heat Rash?
The key is to try to stay cool and avoid sweating a lot. Some tips that can help are:
- Wear loose, lightweight clothes made of cotton.
- Cool off with fans, cool showers, and air conditioning when you can.
- Try to do things outdoors during times of the day when it’s cooler.
Show Sources
UpToDate: “Patient education: Heat rash (prickly heat) (The Basics).”
American Academy of Dermatology: “12 Summer Skin Problems You Can Prevent.”
Cleveland Clinic: “Heat Rash/Prickly Heat.”
Familydoctor.org: “What Is Heat Rash?”
Seattle Children’s: “Heat Rash.”
CDC: “Heat Stress.”
The Merck Manual Home Health Handbook: “Prickly Heat.”
Ely, J. American Family Physician, March 15, 2010.
O’Connor, N. American Family Physician, January 1, 2008.
Habif, T. Clinical Dermatology, 5th ed, Mosby, 2010.
Health Direct: “Summer skin rashes.”
CDC: “Heat Stress – Heat Related Illness.”
