Heat rash (prickly heat, or miliaria) is a harmless but itchy rash of small red or clear bumps that appears when sweat becomes trapped in blocked sweat ducts, usually in hot, humid weather. It often shows up on the neck, chest, back and in skin folds. To treat it, cool the skin, wear loose cotton clothing, avoid scratching, and skip heavy or perfumed creams. It normally clears within a few days. See a pharmacist for products like calamine lotion, and a doctor if it does not improve, spreads, or shows signs of infection.
When temperatures climb, so does the chance of heat rash, a common and uncomfortable skin condition. It is especially relevant in South Africa, where summers can be fiercely hot and humid. The good news is that it is rarely serious and usually settles quickly with simple self-care. Below, Bloom explains how to recognise heat rash, treat it, and prevent it, and when it is worth seeing a professional. If you are looking for cover that supports everyday health, explore health insurance options tailored to your needs.
Key takeaways
| • Heat rash happens when trapped sweat blocks sweat ducts, causing itchy red or clear bumps, often in skin folds. |
| • Anyone can get it, though babies, older adults and people who are very active in the heat are most prone. |
| • Cooling the skin, loose cotton clothing and not scratching are the most effective first steps. |
| • It usually clears within a few days. See a doctor if it lingers, worsens or shows signs of infection. |
What is heat rash?
Heat rash, also called prickly heat or miliaria, develops when sweat becomes trapped under the skin. As your body sweats to cool down, the sweat ducts can become blocked, and the trapped sweat triggers small, itchy bumps a few days later. It is most common in warm, humid conditions.
Anyone can get heat rash, but some people are more prone. Babies are especially susceptible because they cannot regulate their temperature as well and their sweat ducts are still developing. Older adults, people with reduced sweating, those with skin conditions such as eczema, and anyone active in hot weather are also at higher risk.
What triggers it
| • Hot, humid weather. Warm conditions make you sweat more, raising the chance of blocked ducts. This is a real risk in many parts of South Africa. |
| • Tight or synthetic clothing. Fabric that rubs against the skin or traps heat stops sweat from evaporating. |
| • Intense physical activity. Exercise or physically demanding work in the heat increases sweat production and the risk of blocked ducts. |
The three types of heat rash
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Miliaria crystallina. The mildest type, with small, clear, fluid-filled bumps close to the skin’s surface that can break easily. It is usually not itchy. |
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Miliaria rubra. The most common form, often called prickly heat. The blockage sits deeper, causing red bumps and an itchy or prickly feeling. If the bumps fill with pus, it is known as miliaria pustulosa. |
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Miliaria profunda. The least common and most severe type, affecting a deeper layer of skin with firmer, flesh-coloured bumps. It tends to follow repeated bouts of miliaria rubra. |
How to recognise it
The typical signs of heat rash are:
| • Small bumps. Clusters of tiny raised bumps or blisters. On darker skin, the redness may be harder to see, so look and feel for the bumps themselves. |
| • Itching or prickling. An itchy, prickly or stinging sensation that gets worse when you sweat. |
| • Common locations. The neck, chest, back, groin, armpits, elbow creases and other skin folds. |
How to treat heat rash
Most heat rash clears on its own within a few days once the skin cools down. To ease the discomfort, the NHS suggests you:
| • Cool the skin with a damp cloth or a wrapped ice pack for no more than 20 minutes at a time. |
| • Tap or pat the rash instead of scratching it, which can worsen irritation and risk infection. |
| • Wear loose, breathable cotton and keep the area cool and dry. |
| • Avoid perfumed shower gels, and skip heavy creams or ointments that can clog sweat ducts. |
A pharmacist can suggest the best treatment for your situation, which may include calamine lotion or antihistamine tablets to ease itching. Hydrocortisone cream can help too, but it is not suitable for children under 10 without a doctor’s advice. Cool baths or showers, and a soothing oatmeal or aloe vera soak, can also bring relief.
Heat rash is not the same as heat exhaustion
Heat rash is a skin problem, but the same hot conditions can also cause heat exhaustion, which is more serious. Warning signs include dizziness, headache, nausea, heavy sweating, a fast pulse and feeling faint. If someone shows these signs, help them cool down, rest and drink water. If they do not improve within about 30 minutes, become confused, stop sweating, or have a very high temperature, treat it as an emergency and seek medical help immediately.
How to prevent heat rash
| • Stay cool and dry in hot weather, seek shade, and limit time in extreme heat. |
| • Choose light, loose cotton over synthetic fabrics that trap heat. |
| • Stay hydrated so your body can cool itself effectively. |
| • Time outdoor activity for the cooler parts of the day, such as early morning or evening. |
| • Keep skin clean and go for lightweight moisturisers rather than heavy, pore-clogging products in summer. |
When to see a doctor
Heat rash is usually harmless, but see a doctor if it does not improve after a few days, if it keeps coming back, or if you notice signs of infection such as increasing pain, swelling, warmth, pus in the bumps, or a fever. It is also worth getting advice if your baby has a rash and you are worried.
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Frequently asked questions
Stay cool and comfortable
Heat rash is a common part of hot South African summers, but it is easy to manage and prevent. Keep cool, wear breathable clothing, stay hydrated and resist the urge to scratch, and it will usually clear on its own. Knowing when to seek help means you can act quickly on the rare occasion something more is going on.
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