What Is Prickly Heat (Miliaria Rubra)?

What is prickly heat?

The condition that we call prickly heat happens to adults and children when sweat becomes trapped under the skin.

It’s also called heat rash, sweat rash, or miliaria rubra. Children tend to get it more than adults because their sweat glands are still developing.

Prickly heat is uncomfortable and itchy. In most cases, developing the rash isn’t reason enough to see a doctor. There are treatment options and prevention tips for people who frequently get prickly heat.

Symptoms of prickly heat

The symptoms of prickly heat are fairly straightforward. Red bumps and itching occur in an area where sweat has been trapped underneath layers of 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 against 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. This is your skin reacting to the sweat that’s leaked between its layers. Other times the area of your body where sweat is trapped might appear swollen or itch persistently.

In some cases, a person with prickly heat may also develop pustules on their skin. This form of the condition is known as miliaria pustulosa. This may indicate a bacterial infection.

Causes and triggers

Hot weather, particularly alongside humidity, is the most common trigger for prickly heat rash. Your body makes sweat to cool down your skin.

When you sweat more than usual, your glands can become overwhelmed. The sweat ducts may become blocked, trapping the sweat deep underneath your skin. The sweat may also leak through layers of your skin close to the epidermis, or 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 who are used to cooler climates tend to experience heat rash when they travel to tropical places where the temperatures are significantly higher.

Prickly heat on a baby

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 in the folds of their skin around the neck and groin.

Like most baby rashes, prickly heat 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 heat rash.

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?

If your baby displays a fever over 100.4°F (38°C) or other symptoms, call their pediatrician.

How to calm the itchy or prickly feeling

Heat rash, including prickly heat, will often go away without treatment.

The first step to soothing prickly heat is to move away from the irritant (or environment) that’s causing your skin to break out in a sweat. Once you’re in a cooler environment, the sensation of itching underneath your skin might take a while to subside.

Other remedies for prickly heat include:

• wearing light, loose-fitting clothing
• avoiding skin products that contain petroleum or mineral oil
• avoiding perfumed soaps or body care products
• applying a cold compress, which you can make at home using a plastic bag or towel

In some instances, a healthcare professional will recommend triamcinolone 0.1% cream (Triderm). This topical corticosteroid is only available by prescription in the United States. If you have miliaria pustulosa, a healthcare professional will prescribe a topical antibiotic such as clindamycin.

A variety of over-the-counter (OTC) products are also available to help treat prickly heat.

Over-the-counter (OTC) products

Calamine lotion is a natural remedy for prickly heat. It can be applied to the affected area to cool the skin.

Other products to try include:

• OTC corticosteroids, such as hydrocortisone cream in a low dosage
• anhydrous lanolin, a waxy ointment derived from wool
• topical or oral antihistamines to reduce itching

If prickly heat is associated with a fever, you may consider fever reducers such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol). Speak with a healthcare professional before giving one of these medications to a child.

Prevention tips

The most effective way to avoid prickly heat is to stay away from situations that cause excessive sweating. Try these tips:

• Wear loose-fitting cotton clothing if you know you’re going to be in a hot or humid climate.
• Take cool baths or showers frequently if you’re visiting a hot or humid climate.
• If you’re in a hot or humid climate, spend a few hours each day in a cool space with fans or air conditioning.
• Opt for lightweight bedding, such as cotton or linen sheets.
• When you exercise outside, choose gear that’ll wick moisture away from your skin.
• Make sure to change out of sweaty or wet clothing right away after experiencing intense heat.
• Change your baby’s diaper immediately after they wet or soil it.
• Stay well-hydrated by drinking plenty of fluids.

Outlook for prickly heat

Heat rash usually goes away on its own. If the rash seems to be getting worse, or the area seems like it’s becoming infected, consider seeing a doctor.

Remember that bacteria live in your skin. Excessive itching can create an open wound that’ll grow infected as you continue to touch it.

Some people have hyperhidrosis, a condition in which their bodies produce too much sweat. If you suspect you’re sweating too much, you may want to see a dermatologist.

If you notice prickly heat appearing on your skin, 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 (such as dizziness, headache, or rapid heart rate) and move to a cooler area as soon as you can.

This article was reposted with permission from Healthline Media for informational purposes only. The Weather Company and Healthline Media do not provide medical advice, diagnosis, or treatment. See additional information.