What Is Heat Rash in Kids?

Summertime brings so many exciting adventures for kids, from play dates and beach days to ice cream parties and family barbeques. Unfortunately, all that time outside during the hotter months can also bring a pesky, uncomfortable side effect: heat rash. 

Also known as prickly heat or miliaria, heat rash is a bumpy, sometimes itchy, rash that appears on the skin underneath clothing, or in areas where the skin folds.

“Heat rashes are skin eruptions related to occlusion and trapping of sweat within the skin,” explains Florencia Segura, M.D., F.A.A.P. of Einstein Pediatrics in Virginia. When sweat glands become blocked, it causes the skin to break out into small pink or red bumps or blisters.

Here, we will take a look at what heat rash is, what causes it, and how to keep your child’s skin rash-free when the weather heats up.

Types of Heat Rash

Dr. Segura explains that there are two types of heat rash: miliaria crystillina and miliaria rubra. 

“Miliaria crystillina often appears as small, superficial, and fragile clear crystals that can look like beads of sweat on the skin's surface,” she says. “Miliaria rubra, which is more common, can present as small red bumps that, unlike folliculitis or acne, do not involve hair follicles and are often quite itchy.”

She adds that heat rash is generally more frequent during summer and humid weather, or when a child is wearing non-breathable clothing. The rash is more common in newborns due to immature sweat ducts, but it can occur in children of all ages. 

What Causes Heat Rash? 

Heat rash—specifically, the more common miliaria rubra—occurs when the pores at the top of the sweat glands get blocked, explains Brandi Kenner-Bell, M.D., assistant professor of pediatrics and dermatology at Ann & Robert H. Lurie Children's Hospital of Chicago. “You’re not able to secrete sweat normally, so those secretions are trying to get out,” she says.

When sweat becomes trapped in the skin, a rash forms around the duct openings. Hot, humid weather is the main catalyst for heat rash since sweat glands become overworked. Dr. Kenner-Bells adds that many parents tend to overdress their babies (especially during the winter months), causing them to sweat more. Because of this, heat rash can occur any time of the year.

Children with dry skin or eczema who use heavy moisturizers may also experience heat rash, explains Dr. Kenner-Bell. The reason? Creams and moisturizers can form a barrier that prevents sweat from leaving the body, which can lead to a rash—especially when their usage is coupled with hot weather.

For those who breastfeed, lanolin on the nipples can cause heat rash on a baby’s face. Menthol ointments used for a cough can cause the rash to appear on a child’s chest. In older children, a lot of exercise or physical activity can lead to heat rash.

Signs and Symptoms of Heat Rash

In most cases, heat rash in children presents as patches of small pink or red bumps. Dr. Kenner-Bell explains that the bumps can also be skin-colored or appear as little blisters, which can become more inflamed depending on how hot or sweaty the child gets. If the rash is especially red or blister-like, it tends to itch as well.

Heat rash is most commonly located in the folds of the neck, upper chest, arms, legs, and diaper area. A rash that appears on the child’s face is possible but rare, says Dr. Kenner-Bell. 

“Heat rash can last from hours to a few days,” explains Dr. Segura. Its duration depends on its severity and whether the rash is more superficial or severe. Very red, irritated bumps may take several days to clear, points out Dr. Kenner-Bell. 

How to Prevent Heat Rash

In order to keep heat rash at bay, be sure to dress your child in lightweight clothing, such as cotton instead of synthetic fabrics, and keep your children in cooler environments, especially while they sleep. Consider allowing a fan to blow on them, or have your baby just sleep in a diaper if they tend to get hot at night.

Dr. Kenner-Bell also emphasizes how important is to not overdress your baby, since they are unable to tell you if they’re too hot. “Be cognizant of how many layers you’re putting on your baby and how long they’re in their car seat,” she advises.

How to Treat Heat Rash in Kids

“Heat rash can be improved by minimizing heat exposure, reducing humidity, and preventing sweating,” says Dr. Segura. “This can be as simple as moving to a cooler environment, sleeping in a ventilated bedroom, avoiding excessive and tight clothing, and using cold compresses.” Dr. Segura also advises steering clear of synthetic fabrics and opting for more breathable choices, like cotton.

In many cases, heat rash simply needs to run its course, says Dr. Kenner-Bell, adding that you should avoid heavy creams and ointments whenever possible, and never apply powder to the rash, as it is not an effective treatment. 

When to Contact a Health Care Provider About Heat Rash

Aside from visible redness or bumps, heat rash should not produce other side effects, such as a fever. If your child is running a fever in conjunction with their rash, it's a good idea to contact a pediatrician or health care provider. Dr. Kenner-Bell adds that you should also consider calling a health care professional if your child is not drinking or urinating, or is very lethargic.

Of course, you know your child best! If you are concerned the rash is not healing on its own after several days, or if you have questions about its appearance or symptoms, you can always speak with a health care provider for reassurance. 

Heat rash can be uncomfortable for your child, but thankfully, it is a common occurrence that often goes away on its own. By keeping your child dressed in lightweight, cotton clothing and sticking to cooler environments when possible, you can avoid the bumpy, itchy rash that becomes so prevalent during the summer months.