Prickly Heat (Miliaria Rubra)

Medically reviewed by Graham Rogers, MD on April 7, 2017Written by Kathryn Watson on April 7, 2017

What is prickly heat?

The condition that we call prickly heat, also known as heat rash, happens to adults and children when sweat becomes trapped under the skin. Prickly heat is sometimes called “sweat rash” or by its diagnostic name, miliaria rubra. Children tend to be more affected than adults because their sweat glands are still developing.

Prickly heat is uncomfortable and itchy. In most cases, developing a heat rash is not a reason to see a doctor. But there are treatment options and prevention tips for people that get prickly heat frequently.

Prickly heat rash picture

prickly heat

Symptoms

The symptoms of prickly heat are fairly straightforward. Red bumps and itching occur in an area where sweat has been trapped underneath layers of your skin. The neck, shoulders, and chest are the most common places for prickly heat to appear. Folds of skin and places where your clothing rubs your skin are also areas where prickly heat might occur. The area of irritation might display a reaction right away, or it might take a few days to develop on your skin.

Sometimes prickly heat will take the form of a patch of very small blisters, which is your skin reacting to the sweat that has leaked between its layers. Other times the area of your body where sweat is trapped might appear swollen or itch persistently.

Causes and triggers

Hot weather, particularly in conjunction with humidity, is the most common trigger for prickly heat rash. Your body makes sweat to cool down your skin. When you sweat more than usually, your glands can become overwhelmed. The sweat ducts may become blocked, trapping the sweat deep underneath your skin, or the sweat may leak through layers of your skin close to the top layer and become trapped there.

It’s possible to get prickly heat at any time of year, but it’s most common in the warmer months. Some people that are used to cooler climates tend to experience heat rash when they travel to visit tropical places where the temperatures are significantly higher.

Treatment and remedies

Treatments and remedies for prickly heat include:

  • calamine lotion
  • topical steroids
  • anhydrous lanolin
  • wearing loose-fitting clothing
  • avoiding skin products that contain petroleum or mineral oil

The first way to treat prickly heat is to move away from the irritant that is causing your skin to break out in a sweat. Make sure to change out of sweaty or wet clothing right away after experiencing intense heat. Once you are in a cooler environment, the sensation of itching underneath your skin might take a while to subside.

A natural remedy for prickly heat is calamine lotion, which can be applied topically to the affected area to cool the skin. Hydrocortisone cream in a low dosage can also make the feeling of itching subside.

Prevention tips

The most effective way to avoid prickly heat is to stay away from situations that cause excessive sweating. If you know that you are going to be in a hot or humid climate, wear loose-fitting cotton clothing. When you exercise outside, choose gear that will wick moisture away from your skin. Take cool showers frequently when you’re visiting hot and humid climates.

Prickly heat rash in babies

Children, especially infants, are especially vulnerable to prickly heat. Their sweat glands aren’t yet fully developed, and their skin isn’t used to rapidly changing temperatures. Infants tend to experience prickly heat on their face and on the folds of their skin around the neck and groin. Like most baby rashes, heat rash is usually harmless and will go away on its own. Your baby might act cranky and be difficult to soothe while they’re experiencing the itchy sensation of prickly heat.

If you notice a small patch of tiny red blisters beneath your child’s skin, evaluate their surroundings. Are they wearing too many layers? Is their clothing appropriate for the temperature? Is your baby acting restless, and does their urine indicate that they could be dehydrated? A cool bath will provide relief for your child in most situations. Keep the baby’s skin dry when it’s not bath time, and avoid products that are oil-based, which could clog the pores further. If your baby displays a fever over 100.4°F or other symptoms, call your pediatrician.

Outlook

Heat rash usually goes away on its own. If your rash seems to be getting worse, or if it seems like the area is becoming infected, you may want to see a doctor. Remember that bacteria live in your skin, and excessive itching can create an open wound that will grow infected as you continue to touch it. Some people have a condition in which their bodies produce too much sweat, called hyperhidrosis. If you suspect that you’re sweating too much, you may want to be referred to a dermatologist.

If you notice prickly heat appearing on your skin, you may want to be mindful of what your body is trying to tell you. Make sure to stay hydrated in warm climates and during physical activity. Watch for other signs of heat exhaustion (e.g., dizziness, headache, rapid heartbeat) and move to a cooler area as soon as you can.

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