Heat Rash/Prickly Heat

What is a heat rash?

A heat rash is an area of your skin that becomes irritated because of sweat trapped in the pores and pathways (ducts) underneath your skin. As sweat can’t leave your body, a rash forms with tiny pimples or blisters.

Heat rashes are common in hot and humid climates. The rash most often develops areas of your body that don’t get enough airflow or areas where there’s skin-to-skin contact.

What are other names for a heat rash?

Heat rashes are also called:

• Prickly heat rash.
• Sweat rash.
• Miliaria.

Who does a heat rash affect?

A heat rash can affect anyone at any age. Babies, infants and toddlers have a higher risk because their glands and ducts are still growing. They’re also usually well-bundled or in multiple layers of clothing. Sweat causes heat rashes, so people who live in warm and humid climates or athletes are at a high risk as well. Heat rashes can affect people on bedrest when their clothing sits between their skin and another surface for a long period. Fever during an illness may also induce a heat rash.

How common are heat rashes?

Heat rashes affect an estimated 4% to 9% of newborns between 1 and 3 weeks of age. The condition also affects nearly 30% of adults who live in humid climates.

What does a heat rash look like?

A heat rash looks like:

• A group of small red bumps (1 to 2 millimeters), similar to tiny pimples or blisters.
• The skin beneath the bumps is flesh-colored or red to purple.

Where do heat rashes form on my body?

Heat rashes can develop anywhere on your body, but most often appear in creases or folds where skin touches skin. The most common sites of heat rashes include:

• Arms and legs.
• Neck.
• Back.
• Underarms.
• Groin.
• Under your breasts.
• Inner thighs.

Heat rashes also form in areas where your clothing rests on your skin for a long period, like the waistband of your pants. Heat rashes rarely form on your face.

What are the symptoms of a heat rash?

Heat rashes form minutes to hours after you start sweating. The heat rash is an area of your skin with clusters of small, pimple-like bumps. Symptoms of a heat rash include:

• Prickly feeling.
• Mild itch (may be worse with sweating).
• Swelling or skin puffs up around rash.
• Mild pain or a light burning sensation.

Severe symptoms could occur from a heat rash, especially if you itch it and the bumps break open. Reach out to a healthcare provider if you experience the following severe symptoms:

• Rash is warm to the touch.
• Pus or clear fluid leaks from the bumps.
• Severe and persistent itch.
• Severe pain.
• Fever or nausea.

Are heat rashes itchy?

Yes, heat rashes are usually itchy. Most heat rashes have a mild itch or irritation. More rare cases have severe itching that gets worse the more you itch it. As the skin where you have a heat rash is sensitive, the bumps on your skin can break open easily when you scratch. This could lead to an infection. If calamine lotion or a prescribed cream doesn’t alleviate your itch, contact a healthcare provider.

Do heat rashes spread?

Yes, heat rashes can spread on your body. Clogged sweat pathways cause heat rashes to spread. A heat rash isn’t bacteria or a virus that can spread to other people, though; heat rashes aren’t contagious. Rashes usually spread in areas where clothing is tight against your skin, especially when you sweat.

What causes a heat rash?

A clog in the narrow pathways (ducts) that carry sweat to the surface of your skin (pores) causes a heat rash. Your body reacts to the clog and attempts to heal it by creating inflammation that forms a rash.

Many factors cause sweat glands to clog, including:

• Small pieces of dead skin cells (skin secretions) block your gland.
• Too much sweat builds up between your skin and your clothing.
• Hair follicles block your glands.
• Hormone changes; like being on your period.
• Not enough airflow between your skin and clothing.

Heat rashes aren’t caused by being “dirty” or not washing your skin well enough.

How is a heat rash diagnosed?

A healthcare provider will diagnose your heat rash after examining the rash on your skin and asking you questions about your symptoms, especially how long you’ve had symptoms and if any events might trigger the rash, like strenuous physical activity or living in a humid environment.

There aren’t any tests to diagnose a heat rash.

How do I treat a heat rash?

Depending on the severity of your heat rash, you can treat your rash at home by:

• Keeping your skin cool and dry: Use a fan or air conditioner to cool your body down if the temperature is hot or humid. Take a cool shower and either lightly pat your skin dry with a towel or let your body air dry to prevent further irritation.
• Wearing cotton clothing: Choose clothing items made of cotton that allow airflow between the material and your skin. Avoid synthetic materials that often trap heat.
• Eliminating friction: Loose-fitting clothing is best to wear around a heat rash to avoid irritation. For heat rashes around your groin area, you could temporarily avoid wearing undergarments to reduce the amount of clothing rubbing against your rash. Babies should also go a few hours without a diaper for heat rashes that affect their diaper region.
• Using anti-itch medications: If you have severe itching or pain from your heat rash, your healthcare provider might recommend using a corticosteroid cream or calamine lotion to soothe the area.
• Taking medicine to treat any fevers: If your heat rash is induced by fever, try taking an over-the-counter medication, such as Tylenol® or ibuprofen, to bring down your temperature.

How long does it take to get rid of a heat rash?

Once you start cooling your body down, a mild heat rash could go away within a day. On average, heat rashes last two to three days. More severe heat rashes can last up to a couple of weeks without treatment.

If you have a severe heat rash that isn’t going away with at-home treatment and staying cool and dry, contact your healthcare provider.

What shouldn’t I use to treat a heat rash?

Avoid using baby powders, ointments, scented lotions or lotions with petroleum or mineral oils and that could clog your pores and make your heat rash worse.

How can I prevent heat rashes?

You can prevent heat rashes by:

• Wearing lightweight clothing and clothing that doesn’t cause friction by rubbing on your skin.
• Wearing clothing made of cotton and avoiding synthetic fabrics.
• Staying in environments with airflow (fans) or an air conditioner if it’s hot.
• Keeping your body cool and dry.
• Staying hydrated and drinking plenty of water.
• Avoiding excessive activity in very hot or humid temperatures.

What can I expect if I have a heat rash?

Heat rashes can irritate your skin, which can be itchy or sometimes painful. The rash, on average, will last two or three days. Keeping the affected area of your skin cool and dry is the best treatment. Try not to itch your rash, and use calamine lotion to calm your skin. Make sure you don’t use powders or creams that’ll clog your pores to prevent the rash from becoming more irritated.

If you experience severe symptoms or believe you have an infected heat rash, contact a healthcare provider immediately.

When should I see my healthcare provider?

If you experience any severe symptoms of a heat rash, contact a healthcare provider. Severe symptoms include:

• Pain.
• Intense itching.
• Rash feels warm to the touch.
• Rash becomes infected (leaks pus or fluid, swelling, fever, nausea).
• Rash doesn’t go away after at-home treatment or persists for longer than a week.

What questions should I ask my doctor?

• Do I need a prescription lotion to treat my heat rash?
• Are there any side effects from the treatment you recommend?
• Can I continue exercising if I have a heat rash?
• What should I do if I get frequent heat rashes?