What does a heat rash look like? How to identify and treat it

Heat rash is a common skin problem in the summer, when sweat gets trapped underneath your skin. Heat rash on adults strikes in areas where your skin folds over itself, such as the armpits, groin and beneath the breasts.

"Sweat is the way the body cools itself, but at the same time, too much sweating or sweat trapped below the skin can be irritating," Dr. Anne Chapas, member of the American Academy of Dermatology and a board-certified dermatologist based in New York City, tells TODAY.com.

What is heat rash?

Heat rash, which is also known as prickly heat or miliaria, is skin irritation that develops when sweat is trapped under the skin. It can look like blisters or lumps and can be very itchy.

"When there's too much heat and humidity, the sweat glands can clog up," Dr. Danny Del Campo, member of the American Academy of Dermatology and board-certified dermatologist based in Chicago, tells TODAY.com. "You’re sweating so much, and your skin can't breathe." Your body tries to pump out more sweat, but it can't, so you develop an inflammatory state with redness and sometimes bumps and blisters.

"We’re all sweating, especially if we’re working out. It's easy to get heat rash in places where skin touches other skin," Dr. Anthony Rossi, member of the American Academy of Dermatology and board-certified dermatologist based in New York City, tells TODAY.com.

"It's a very, very normal thing that can happen," NBC News medical contributor Dr. Natalie Azar said in a TODAY segment on May 31.

Heat rash is especially common in babies. It can develop when they are overly swaddled since their immature sweat glands aren't fully formed, so moisture can't evaporate as well as it can in adults.

In adults, heat rash usually appears in the folds of the skin and where clothing comes in regular contact with the skin, according to Mayo Clinic. Exercising in hot weather can be a cause of heat rash, as workout clothes are often tight and not that breathable.

The most commons symptoms of heat rash are small, itchy red bumps and blotches. Sometimes, you can get fluid-filled sacs. Heat rash usually comes on quickly — within hours after you get hot and sweaty. Mayo Clinic explains that heat rashes can look like the following:

A group of small bumps that can look like pimples or blisters and are fluid-filled and may break open

Deeper bumps in the skin that itch or prickle

Pus-filled bumps

Bumps similar to goosebumps that may break open

It's important not to scratch your heat rash, since scratching can damage the skin and introduce bacteria that can cause an infection.

The best ways to get rid of heat rash fast involve keeping your skin cool and avoiding additional sweat.

Get out of the heat. Azar recommended getting to an air-conditioned, cool environment to cool your body down.

Take a cool shower, pat your skin dry with a towel or let your body air dry. You can also try cool compresses.

Avoid excess sweating. For example, don't exercise and try to avoid being outside if it's hot and humid.

Change into loose, breathable clothing. Wearing loose clothing and not too much clothing can help your body cool down and dry off, Azar said. Avoid clothing in synthetic materials. For babies suffering from heat rash around the groin or buttocks, consider removing their diaper.

Use antihistamines. This is especially helpful if your rash is itchy, Azar said. You can use a cream or take them by mouth.

Use a moisturizer, anti-inflammatory lotion like calamine lotion, or over-the-counter steroid creams. Keep your moisturizers in the fridge for a maximum cooling effect, Del Campo suggests.

Try oatmeal. Azar said that you can make an oatmeal paste at home or put it in the bath and soak.

Preventing heat rash

You’re less likely to develop a heat rash if you stay cool and dry, so many of the tips to treat heat rash quickly are similar to those to prevent it altogether.

Choose your exercise clothes wisely. Wear clothing that wicks away sweat so you’re not trapping sweat against your skin. Cotton doesn't irritate your skin, but it doesn't wick away moisture either. "Newer sports fabrics do a good job of wicking moisture away, but they are very compressing against skin. If you leave them on too long you can break out in a heat rash," Rossi says.

Keeping your skin cool and dry. "The most important thing is to change out of those sweaty clothes quickly," Chapas says. "Take a cool shower to cool down your body and change into a clean shirt."

Wear lightweight clothing, especially clothes that don't rub against your skin.

Try to stay in cool environments when it's hot out. Avoid exercising when it's super hot.

Stay hydrated.

Use antifungal powders, especially in your groin folds and armpits, to help absorb moisture.

Once your body cools down, your heat rash will go away within one to three days, according to the Cleveland Clinic. Heat rashes that turn into pimples can take longer. If your rash isn't getting better in a few days after using at-home treatments, see a doctor.

If your heat rash seems to be getting worse after at-home treatments or is showing signs of infection — such as draining, redness, fever, nausea or increased pain, especially in children, who may be more prone to scratching the rash — see a health care provider.

A rash that's not clearing up could be another type of rash, bug bites or a viral infection. "If your rash isn't associated with sweating or is spreading to other parts of your body like your chest, back or legs, it could be something else," Chapas says.

Heat rash can also be a warning sign that you’re overdoing it in the warm weather. Don't ignore it — overheating can also lead to heat stroke and heat exhaustion. And too much time in the sun can cause sunburn and sun poisoning.

This article was originally published on TODAY.com