Prickly heat – or miliaria rubra, to give the medical term for the most common type – is a rash with tiny, often red bumps that appears under your skin. The other main symptoms you’re likely to notice are itching, or a prickly feeling. These bumps can appear anywhere on your body, but tend to crop up where your clothes rub against your skin.
These itchy/prickly bumps can appear a few days after being overheated. They usually disappear a few days after returning to a cooler climate.
Prickly heat often develops when you are very hot and sweating more than usual. This can happen if the temperature is very high – such as when you’re on holiday abroad. It can also develop if you are hot and sweating for other reasons – if you are wearing too many clothes, or are overweight or obese.
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Prickly heat can also happen in winter, if you have the heating on very high. Even something as simple as sitting too close to a heat source, like a radiator, can cause this condition. You can also develop prickly heat if you have been unwell and have had to spend more time in bed than usual.
Tips for skin disorders
What causes prickly heat rash?
Prickly heat rashes develop when your sweat ducts become blocked. We have thousands of sweat glands just below the surface of the skin, and if the ducts become blocked the sweat can’t escape, so leaks out into your skin instead. This causes the bumps that create the itchy or prickly rash.
Types of prickly heat rash
Miliaria rubra is the most common type of prickly heat rash. It's itchy, prickly and clearly visible as tiny bumps (usually red) under the skin, especially where clothes rub.
Miliaria crystillina is the least itchy and produces small, clear spots. These tend to vanish quite quickly – usually within a few days.
Miliaria profunda is usually only found in places with a hot climate. People who have had miliaria rubra often can develop this. The symptoms are larger lumps, but very little itching. However people with this condition may develop heat exhaustion and fever if the rash covers large areas of their skin.
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Prickly heat rash treatment
The symptoms of prickly heat – itching and prickling - may drive you to distraction, but it isn’t a serious condition. You should be able to make yourself more comfortable with these self-help tips, and perhaps a trip to a pharmacy.
Try to keep cool. This may seem difficult if you’re somewhere hot, or we are in the grip of a heatwave at home, but a few simple steps should help.
- Stay in the shade and out of the heat as much as you can, but especially during the middle of the day when the temperature is likely to be hottest.
- Air conditioning is a really good way to stop you sweating and making the prickly heat worse. If you’re on holiday your hotel might have air conditioning in its bedrooms, lobby and restaurants. If you’re at home, an electric fan can help to keep you cool.
- A cool bath or shower can also cool you down enough to reduce sweating.
- Keep drinking fluids, to make sure you don’t risk becoming dehydrated. Keep a bottle of water with you if you are out and about.
- Choose your clothes carefully. Avoid synthetic fabrics, as these are likely to make you sweat more. You are likely to be most comfortable in loose, clothes made of cotton, or another natural fabric. Some higher-tech clothes are made out of breathable fabrics that wick the sweat away from your skin. In the privacy of your home or hotel room, wearing as little as possible could help keep you cool too.
- Talk to your pharmacist. (If you are on holiday ask your hotel to recommend a local pharmacy.) They should be able to suggest products that could help you feel more comfortable.
If you have suffered with prickly heat in the past, talk to your pharmacist before you go away. Calamine lotion and 1% hydrocortisone cream may help relieve your itchy skin and your pharmacist may have other recommendations.
It’s also worth asking about antihistamine tablets, as these can help if your skin is very itchy. It is important to check with your pharmacist or GP first, however, to make sure that none of these products are likely to react with medicine you are already taking.
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