Learn more about the symptoms, causes and treatment of this heat-related problem of the skin that affects people of all ages.
Heat rash — also known as prickly heat and miliaria — isn't just for babies. It affects adults, too, especially in hot, humid conditions.
Heat rash occurs when sweat is trapped in the skin. Symptoms can range from small blisters to deep, inflamed lumps. Some forms of heat rash are very itchy.
Heat rash usually goes away once the skin cools down. Severe forms of the condition might need treatment from a health care provider.
Adults usually develop heat rash in skin folds and where clothing rubs against the skin. In infants, the rash is mainly found on the neck, shoulders and chest. It can also show up in the armpits, elbow creases and groin.
The types of heat rash are classified according to how deep the sweat is trapped in the skin. Signs and symptoms for each type vary.
Heat rash usually heals by cooling the skin and avoiding exposure to the heat that caused it. See your health care provider if you or your child has symptoms that last longer than a few days or the rash seems to be getting worse.
Heat rash develops when a duct that leads from a sweat gland to the surface of the skin is blocked or inflamed. This then blocks the opening of the sweat duct on the surface of the skin (sweat pore). Instead of evaporating, sweat is trapped beneath the skin, causing irritation and bumps on the skin.
Factors that increase the risk of heat rash include:
Heat rash usually heals without scarring. People with brown or Black skin are at risk of spots of skin that get lighter or darker in response to inflammatory skin conditions (postinflammatory hypopigmentation or hyperpigmentation). These changes usually go away within weeks or months.
A common complication is infection with bacteria, causing inflamed and itchy pustules.
To help protect yourself or your child from heat rash:
You don't need tests to diagnose heat rash. Your health care provider is usually able to diagnose it by examining the skin. A condition that looks like heat rash is transient neonatal pustular melanosis (TNPM). TNPM mainly affects newborns with brown or Black skin. It's harmless and clears up in a couple days without treatment.
Treatment for mild heat rash is cooling the skin and avoiding exposure to the heat that caused the condition. Once the skin is cool, mild heat rash tends to clear quickly.
Tips to help your heat rash heal and to be more comfortable include the following:
A visit with a health care provider usually isn't necessary for heat rash. If your rash is more severe, you may want to see your primary care provider or a doctor who specializes in skin disorders (dermatologist) to be sure it's heat rash and not another skin disorder.
Before you go, it's a good idea to list questions you have about your condition. For heat rash, questions to ask your health care provider include: