10 effective heat rash treatment tips

Dr Roger Henderson
·7-min read
Photo credit: Getty Images
Photo credit: Getty Images

Covered in itchy bumps after a day in the sun? Sounds like you might have a case of heat rash. If you've been exercising, sweating heavily or simply sunbathing it is common for prickly heat rash to occur. The good news is heat rash is not usually serious and can be treated easily at home.

Dr Roger Henderson looks at heat rash symptoms, causes and treatment tips:

What is heat rash?

Heat rash, medically known as miliaria rubra, is a condition that occurs when sweat becomes trapped under the skin. Also known as prickly heat or sweat rash, heat rash usually affects people who sweat a lot and is caused by blockage of the sweat ducts found just under the surface of the skin. If these become blocked, sweat slowly seeps into the nearby skin and causes localised skin inflammation and an itchy rash.

Heat rash risk factors

Doing anything that makes you sweat can increase your chances of prickly heat rash, but the following are particular heat rash risk factors:

• Babies and children

Heat rash can occur at any age but is particularly common in young babies. It is more common in children than adults because their sweat glands are still developing.

• High temperatures

In adults heat rash often occurs when people sweat more – either during a heatwave or when abroad in hot climates – and around a third of travellers can be affected by prickly heat because of this.

• Increased sweating

Heat rash may also occur in cooler countries if sweating continually occurs over one part of the body, such as the back if someone has to lie on their back for extended periods of time or if bedclothes are too heavy and warm.

Photo credit: ARISA THEPBANCHORNCHAI - Getty Images
Photo credit: ARISA THEPBANCHORNCHAI - Getty Images

What causes heat rash?

Heat rash occurs when sweat glands become blocked. Anything that blocks sweat glands – such as tight bandages or excessively tight clothing worn for too long – may trigger prickly heat in that area.

Some people do seem to be more at risk of developing heat rash, possibly because of the action of a particular skin germ (bacteria) called Staphylococcus epidermis. This completely harmless bacteria found on the skin is capable of secreting a slightly sticky substance and if this is combined with dead skin cells and sweat it can block sweat ducts. Many people with prickly heat are found to have more Staphylococcal epidermis bacteria present than in people who do not usually suffer from it.

Heat rash symptoms

Heat rash symptoms are usually straightforward, with small red bumps and itching developing in the area that has been sweating. The rash tends to be in certain areas only and does not usually spread across the body.

Heat rash symptoms usually include the following:

  • Small, raised spots

  • Itchy and prickly skin

  • Mild swelling

The most common areas affected by heat rash include the chest, shoulders and neck as well as in the folds of skin in overweight people.

Types of heat rash

There are a number of different types of prickly heat rash:

• Miliara rubra

This is the usual type that is most commonly seen, where the sweat ducts block in a deeper part of the skin. The spots that develop are tiny and may look like small blisters, with areas of the skin where clothing has rubbed often showing patches of spots. Itching or a prickling feeling on the skin is common, and the rash often takes a few days or even weeks to develop after sweating has started although it is usually quicker to settle when out of the hot environment. Where the sweat ducts have become blocked to cause the rash there is often very little or no sweat at all, and you may feel unusually uncomfortable when in the sun or a hot atmosphere. If miliaria rubra is very widespread then heat exhaustion can occasionally occur because the body is not able to get rid of body heat by normal sweating.

• Miliaria crystalline

If the sweat ducts are very close to the skin surface, this is the more likely type of prickly heat that will develop. The spots here are often more clear than in miliaria rubra – and may be confused with beads of sweat - and do not last as long, often disappearing after a few hours or a day or two from when they first appear. Many people have few if any other symptoms and there may be no itch at all.

• Miliaria pustulosa

If the heat rash skin spots become infected, pus can develop in them causing this type of prickly heat that can occasionally be tender and weep infected fluid.

• Miliaria profunda

This is a much less common type of prickly heat and is when the sweat ducts block in the middle layer of the skin called the dermis. It usually only occurs in people who have had repeated episodes of prickly heat rash and who live in a hot climate all year round. The spots are bigger, more flesh-coloured but often do not itch.

10 heat rash treatment tips

Simple cooling measures are all that is normally required to treat heat rash, but if the skin rash causes discomfort or is slow to settle, there are a number of ways to help treat it:

1. Stay cool

Keeping the skin cool so it doesn't sweat is the best way to help heal heat rash.

2. Wear loose cotton clothing

Always wear loose cotton clothing, or clothing with breathable fabric. Avoid tight-fitting and nylon clothing that can make sweating worse.

3. Moisturiser

Some moisturising creams do seem to help with heat rash. Opt for creams that contain anhydrous lanolin to help prevent the sweat ducts from blocking.

4. Steroid creams

Over-the-counter mild steroid creams such as hydrocortisone 1% can be very effective at reducing skin irritation and inflammation, but this should not be used on the face.

5. Calamine lotion

If simple creams such as calamine lotion are used to help soothe the skin, you may need to use a moisturising cream afterwards to stop the skin from drying - always avoid skin products that contain petroleum or mineral oils.

6. Antihistamines

Over the counter antihistamines (such as Benadryl) can also be taken to reduce symptoms of a sweat rash.

7. Cold compress

For irritation or discomfort from the rash, apply cold compresses to the area such as a cool flannel or ice wrapped in a cloth but never apply ice directly onto the skin.

8. Oatmeal

Oatmeal can help soothe irritated skin and the easiest way of using this is to put 1 or 2 cups of oatmeal in a lukewarm (not hot) bath and soak for 20 minutes. You can also do this by adding 3 to 5 tablespoons of baking soda to a lukewarm bath and soaking for about 20 minutes.

9. Aloe vera

Aloe vera is a natural anti-inflammatory product that can cool down the skin and help prevent infections, and is known to be helpful in soothing the swelling and discomfort of heat rash when it is applied in gel form directly onto the rash.

10. Pat don't scratch

Avoid scratching the rash as much as possible as this will exacerbate your symptoms – tap or pat the rash if it itches.

Heat rash in babies

Because the sweat ducts in babies and young children are not fully developed they are more likely to experience a sweat rash than adults, as their skin is slower to adapt to changes in temperature.

Prickly heat rash is usually seen on the face and around the groin and neck in babies. Although it is completely harmless, it can cause irritation and a grumpy baby!

Keeping baby cool and making sure their clothing is appropriate for the temperature may be enough to settle symptoms. Avoid oil-based skin products, as they can further block the sweat ducts. Simple calamine lotion can help cool and soothe irritated skin.

Heat rash prevention tips

The best way to prevent heat rash is to keep your skin cool so you do not sweat:

✔️ For most people, simply keeping away from high temperatures and situations that may cause excessive sweating is enough to prevent it from occurring – even doing this for several hours a day can help.

✔️ Make sure you stay well hydrated in warm temperatures, and when exercising choose sportswear that will wick moisture away from the surface of your skin.

✔️ If you abroad in a hot and humid country or there is a heatwave at home try to take a cool shower frequently and read our essential heatwave hacks to help you cool down.

Last updated: 28-04-2021

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