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Prickly heat rash

Prickly heat rash, also called miliaria, is a rash that can develop after a person sweats far more than usual and sweat glands become blocked.

Babies and children can also get prickly heat rash during hot or humid weather because their sweat glands are not fully developed.

Prickly heat causes an itchy rash of small red raised red spots with a prickling or stinging sensation.

Prickly heat usually affects parts of the body covered by clothes, such as the back, abdomen, neck, upper chest, groin or armpits.

Heat rash on a baby's shoulder

Image: Copyright © ISM / Phototake

Prickly heat usually clears up on its own within a few days. However, in serious cases heat rash can interfere with the body's heat-regulating mechanism and cause heat exhaustion.

Heatstroke is a more serious condition when the body can no longer cool itself. This is a medical emergency.

What causes prickly heat rash?

heat rash

Heat rash begins with excessive perspiration, usually in a hot, humid environment. The perspiration makes it easier for dead skin cells and bacteria on the skin to block the sweat glands, forming a barrier and trapping sweat beneath the skin, where it builds up, causing the characteristic bumps. As the bumps burst and sweat is released, there may be a prickly, or stinging sensation that gives this condition its name.

What are the symptoms of heat rash?

Small, itchy red bumps on the skin are the symptoms of heat rash. The rash may feel prickly, stinging or burning.

Seek medical advice if:

  • Heat rash does not go away on its own within a few days.
  • You develop an infection in an area where you recently had heat rash.

What are the treatments for heat rash?

In most cases, heat rash will clear up on its own in a few days if the affected area is kept cool and dry. Avoid excessive heat and humidity and cool off with a fan, take a cool shower or bath and let your skin air dry, or if you have air-conditioning, use this to cool yourself. Once the skin is cool and dry again, don’t use any type of oil-based product, which might block your sweat glands. Calamine lotion and/or hydrocortisone cream can relieve itching and irritation.

If your prickly heat does not go away within a few days, or if you develop an infection where the bumps have burst, you may need medication, so so seek medical advice.

How can I prevent heat rash?

To prevent heat rash, avoid situations that can lead to excessive sweating, such as hot, humid environments and strenuous physical activity. In hot weather, use fans and cool showers and baths to stay cool, or air conditioning if available; dry your skin thoroughly; and wear lightweight, loose-fitting clothes ideally made from cotton.

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WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on November 26, 2013

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