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

As warm weather ramps up across much of the U.S., it's time to start taking precautions to protect yourself during long days spent in the sun. That means taking shade when possible, wearing sunscreen and sun-protective clothing and learning how to get rid of a heat rash fast.

Heat rashes are a common summer skin problem caused by excessive sweating to the point that the sweat gets trapped under the skin. Adults most often develop heat rashes on parts of the body where the skin touches, like armpits, ground and under 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 is also called prickly heat or miliaria. The common condition is defined as when the sweat glands and ducts get blocked, leading to the sweat to flow back into the outer (epidermis) and middle (dermis) layers of skin.

“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.”

When your body is unable to pump out more sweat, the skin can become red and inflamed. Heat rash may also look different from other rashes you've had in your life. For example, it can look like a blister or just groups of bumps. It can be itchy, though you shouldn't scratch to minimize the risk of infection.

“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.

While adults can get heat rashes, the highest-risk group is infants. That's because they have immature sweat glands, are less able to regulate their body temperature, have more skin folds and are often swaddled. Babies most often experience heat rash in their armpits, neck, groin, thighs and bum.

Adults may develop heat rash in all these places too, but it's most common in skin folds and places that are covered by clothes since this can impact the sweat glands, per Mayo Clinic.

Anything that causes excess sweating can lead to heat rash, but one common situation is exercising outdoors in high temperatures with tight, not breathable clothing.

What does heat rash look like?

Most often, a heat rash will take the form of small red bumps in splotches around your body. They can itch and be filled with fluid. Heat rashes usually appear suddenly within a few hours of sweating excessively. Common characteristics of heat rashes include:

• 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

One of the toughest parts about heat rashes is that they itch. But it's important not to scratch because if you cause an open wound, that can allow bacteria in and cause an infection.

How to get rid of heat rash quickly

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.

How to prevent 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.

How long does heat rash last?

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