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" or "sweat rash." Your doctor might call it "miliaria."
Anyone can get a heat rash, but it's more common in babies and young children.
Types of Heat Rash
There are three types of heat rash:
Miliaria crystallina: This is the mildest type. It happens when the sweat ducts (pores) on your skin's surface get clogged. It usually looks like clear bumps filled with fluid. The bumps can break easily.
Miliaria rubra: This type is often referred to as prickly heat, because it can cause an itchy or prickly feeling along with small, inflamed bumps on your skin. If the bumps become filled with pus, your doctor will call it miliaria pustulosa.
Miliaria profunda: This type affects the skin's deepest layer. The bumps in this type of heat rash look like goose bumps and are firm and painful or itchy. They may break open.
What Causes a Heat Rash?
Heat rash happens when the ducts beneath your skin that transport your sweat get clogged up. The sweat can't get through the pores in your skin, and it causes your skin to get irritated. Then a rash develops.
This is most often caused by:
- Small pieces of dead skin cells getting trapped in your pores
- Sweat collecting between your skin and your clothing
- Hair follicles blocking your sweat glands
- Hormonal changes, like having your period
- Not enough airflow between your skin and clothing
What Does a Heat Rash Look Like?
Heat rash looks like tiny raised bumps surrounded by red, irritated skin. On darker skin tones, the redness may be less noticeable, or it may look darker.
Heat rash usually happens on your:
- Elbow creases
Heat rash on face
Babies sometimes get heat rashes on the face, but for adults, it's more rare. When an adult gets a face rash, it might be because of trapped heat and sweat from face masks. To avoid this, try to gently clean your face after wearing a mask.
Heat rash under breast
Heat rashes tend to form where skin rubs together, like underneath your breasts. This can lead to a sore rash called intertrigo. It tends to affect people who have large breasts. To avoid it, try patting the area dry with a clean towel. You can also wear a well-fitting, cotton bra.
How Long Does a Heat Rash Last?
Heat rash 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 especially true if you sweat.
You don't have to worry about spreading a heat rash to other people, though. It's not contagious.
Heat Rash Risk Factors
Some things can make you more likely to get a heat rash. These include:
Frequent exercise. Physical activity makes you sweat. Too much sweat can clog your sweat ducts.
Hot, humid weather. When it's hot, your body sweats to stay cool. Up to 30% of people living in warm climates get heat rashes.
Bed rest. Staying in one position can trap sweat between your clothes and skin and cause irritation.
Fever. This can cause you to sweat, especially if you stay in bed while you’re feeling sick.
Being a newborn. Up to 9% of newborns get it in their first few weeks of life. Young babies have a harder time controlling their body temperature than adults. This might be partly because they don't have fully developed sweat ducts. These immature ducts are more likely to get clogged.
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:
- Cool your body in an air-conditioned room or with a fan
- Take a cool shower or bath and let your skin air-dry
- Wear fewer layers of clothing
- Wear loose clothing that allows airflow
- Choose cotton fabrics, which are more breathable
- Don't scratch your skin, or it could become infected
- Keep your skin dry
- Try an anti-itch cream like calamine lotion
- Take medication to lower a fever, if that's what's causing your heat rash
- Try to shift your position and change your clothes often if you are on bed rest
If you develop an infection where the bumps have burst, you may need medication, so call your doctor. Also call the doctor if you have a fever or any other signs of illness.
How to get rid of heat rash quickly
Heat rash tends to go away on its own in 2 to 3 days. Some home remedies, like the ones described above, can help speed up the process. But there isn't a single quick fix for heat rash.
In the meantime, the first step is to cool down. This won't make the heat rash go away, but it can immediately help with the itchiness it causes.
Heat rash cream
There are some creams that can help with heat rash. They're not made specifically for heat rash, but help with general skin irritation and itching. These creams are available over the counter, so you don't need a prescription.
Best Cream for Heat Rash
The best creams for heat rash are calamine lotion and corticosteroid cream. One common type of corticosteroid cream is 1% hydrocortisone cream (this is different from hydrocortisone ointment, which can clog sweat glands). Talk to a doctor before using hydrocortisone cream for children under 10 or if you are pregnant.
Baby Heat Rash Treatment
Heat rash in young children can look uncomfortable, but it's usually not serious.
To treat your baby's symptoms:
- Give them a cool bath and pat them dry gently
- Put them in an air-conditioned room, or position a fan so that a gentle breeze blows over them
- Avoid creams or ointments that may irritate the skin
Call your pediatrician if:
Heat Rash Prevention
You can't always prevent heat rash, but there are things you can do to significantly lower your risk:
- Avoid situations that can lead to excessive sweating, such as hot, humid environments.
- Avoid strenuous exercise when it is very warm.
- Try to do things outdoors during times of the day when it's cooler.
- In hot weather, use air-conditioning, fans, and cool showers and baths to stay cool.
- Dry your skin thoroughly after showering or swimming.
- Wear lightweight, loose-fitting clothes made of cotton.
- Avoid wearing synthetic fabrics.
- Drink plenty of fluids to cool the body and to keep hydrated.
When to Call Your Doctor About a Heat Rash
Call your doctor about a heat rash if:
- The rash is severe or painful or does not go away on its own within a few days
- You get an infection in an area where you recently had heat rash
- You have a fever or any other signs of illness
- The rash is bright red or has streaks
- The rash starts after you have been taking an antibiotic or new medication
- The rash leaks pus or forms scabs
Most heat rashes will get better on their own without any complications. Sometimes, heat rashes can get infected. Look for signs like fever, swelling, or pus leaking from the rash. If this happens, your doctor may prescribe antibiotics. If you have darker skin, you might notice lighter or darker spots that last a few weeks to months.