Heat rash

Page last reviewed: 13/07/2011

Prickly heat is an itchy, red rash that often causes a stinging or prickling sensation on the skin.

It usually occurs when you sweat more than usual, for example in a hot or humid climate, but it can also occur in winter. People often experience it when abroad on holidays. See causes of prickly heat for more information.

Excessive sweating can cause your sweat glands to become blocked, which can trap sweat beneath your skin. This causes irritation, and results in the rash.

The rash can occur anywhere on your body, but it most commonly affects areas that are covered by clothing.

Who is affected

People who are overweight or sweat easily are more likely to get prickly heat.

Babies and children are also more prone to prickly heat because their sweat glands are not fully developed.


Prickly heat is not a serious condition, and rarely requires any specific treatment. However it can be very uncomfortable. Most prickly heat rashes will heal within a few days.

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Page last reviewed: 13/07/2011

The symptoms of prickly heat tend to appear a few days after exposure to hot temperatures. But occasionally, symptoms do not appear for several weeks or months.

The rash

Prickly heat causes a rash to form on your skin. The rash is normally made up of tiny spots or bumps, surrounded by a patch of red skin. Sometimes, the spots look like tiny blisters. This rash may cause:

  • mild swelling
  • itching
  • a stinging or intense prickling sensation

The rash can affect any part of your body, but most commonly appears on your:

  • back
  • abdomen (tummy)
  • neck
  • upper chest
  • groin
  • armpits
  • hands
  • feet

If you have prickly heat, your symptoms are usually worse on the areas of your body that are covered by clothing. This is because your clothing can cause friction and make you sweat more often.

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Babies and rashes

If your baby has a rash and appears to be unwell, speak to your GP for advice. Heat rash is a common condition in babies and does not cause any serious harm. However, if you are concerned, your GP will be able to confirm the cause of your baby's rash and give appropriate treatment.

Page last reviewed: 13/07/2011

Prickly heat occurs when your sweat glands become blocked.

If you sweat excessively, it is easier for dead skin cells and bacteria on your skin to collect in your sweat glands. If these glands become blocked, the sweat is trapped underneath your skin in tiny swollen pockets. It also seeps into the nearby tissue and irritates your skin.

When the pockets burst and release sweat, this causes a stinging, prickling sensation that gives the condition its name.

Causes of prickly heat

Prickly heat is usually caused by being in a hot climate, which makes you sweat more than usual.

Other causes are:

  • Spending long periods of time in bed (due to an illness or a long-term health condition, for example). Immobility and illness can make you sweat, especially if you have an electric blanket and other warm bedding.
  • Wearing too much clothing in winter.
  • Sitting too close to a fire or heater.


Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease, while other bacteria are good for you.
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

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Page last reviewed: 13/07/2011

Prickly heat is not a serious condition and rarely requires any specific treatment. Most rashes will disappear naturally after a few days.

However, there are a number of steps you can take, which may ease your symptoms:

  • Avoid excessive heat and humidity where possible. Spend some time in the shade, or take a small fan outside with you. Being exposed to heat will only make you sweat more, and could make your rash worse.
  • Wear loose cotton clothing. Avoid wearing synthetic fibres, such as nylon and polyester, as they trap heat more easily than natural fibres.
  • Keep your skin cool. Taking a cool bath or shower will help to prevent sweating and soothe your skin. You will get considerable relief if you can avoid sweating for a few hours a day by staying in an air-conditioned room.
  • Calamine lotion can be used on sore and irritated skin. It will help cool and soothe your skin. You can buy it at most pharmacies.
  • Hydrocortisone cream can treat a rash that feels particularly itchy and irritated. You can buy low-strength hydrocortisone cream from your local pharmacy. However, avoid using this cream on your face, and always follow the instructions. You should not use it for prolonged periods without medical supervision.

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Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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