What causes prickly heat?

It happens when sweat ducts become blocked in hot, humid conditions, so sweat is trapped under the skin and causes tiny itchy or prickly bumps or blisters. It is not an infection and is very common in Singapore’s climate and in babies.

How do I get rid of heat rash quickly?

Cool the skin – move somewhere cooler, take a cool shower and let skin air-dry – wear loose, breathable cotton clothing, and avoid thick creams that block the skin. Calamine or a cool compress soothes itch. It usually clears in a few days.

Should I put cream on prickly heat?

Heavy, greasy creams can make it worse by further blocking sweat ducts. A light calamine lotion or a cool compress can ease itch, but the main treatment is cooling and drying the skin rather than applying thick products.

Why do I keep getting heat rash in Singapore?

The persistent heat and humidity make you sweat heavily and slow evaporation, so ducts block easily – especially under tight or synthetic clothing. Staying cool, wearing loose cotton and reducing heavy sweating in the heat helps prevent it.

When should heat rash be seen by a doctor?

See a doctor if it does not improve after a few days, keeps coming back, shows signs of infection (spreading redness, pus, fever), or if you are unsure it is heat rash. Seek urgent help if someone has heat exhaustion or heat-stroke symptoms.

Prickly Heat / Heat Rash (Miliaria) Singapore

Written & reviewed by the BestDoctors.sg editorial team · Last updated 1 Sep 2026 · General information, not medical advice

Quick answer. Prickly heat, also called heat rash or miliaria, is a common, harmless rash that appears when sweat gets trapped under the skin because the sweat ducts are blocked. It causes clusters of tiny red bumps or clear blisters with a prickling, stinging or itchy feeling, usually where sweat collects – the neck, chest, back, skin folds, and areas covered by tight clothing. It is very common in Singapore’s hot, humid climate and in babies. The mainstay of treatment is simple: cool down, keep the skin dry and let it breathe. It usually clears within a few days once the skin cools.

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The core idea: prickly heat is a “too hot, too sweaty” rash. Cooling the skin and reducing sweating is both the treatment and the prevention – creams are rarely the main answer.

What prickly heat is

Your skin is covered in tiny sweat glands that release sweat through narrow ducts opening at the surface. When you cool down, that sweat evaporates and carries heat away. In hot, humid conditions – or under clothing and creams that seal the skin – the ducts can become blocked, so the sweat cannot escape. Instead it leaks into the surrounding layers of skin, where it irritates the tissue and produces the small bumps or blisters and the characteristic prickling feeling.

Prickly heat is a nuisance rather than a danger. It is not an infection, not contagious, and not caused by poor hygiene. It is simply a sign that the skin has been too warm and too damp for the sweat ducts to work normally. Once the skin cools and dries, the ducts clear and the rash fades, usually leaving no mark. Because the trigger is heat and trapped sweat, the same rash can return whenever conditions are hot and humid again – which, in Singapore, can be much of the year.

Symptoms and types

Doctors group heat rash by how deeply the sweat is trapped, and the depth changes how it looks and feels:

The mildest form shows as very superficial, small clear blister-like spots that break easily. They are usually not itchy or sore and often clear quickly once you cool down (miliaria crystallina).
The common form is a crop of small red, itchy or prickly bumps, sometimes stinging or burning. This is the type most people mean by “prickly heat” (miliaria rubra).
A less common form produces deeper, firmer, flesh-coloured bumps and tends to appear after repeated bouts of the red form.

The rash favours areas that sweat heavily or where clothing rubs and holds heat in – the neck, upper chest and back, in skin folds and the groin, and under waistbands, collars, straps or tight bands. In babies it often appears on the face, neck, shoulders, skin creases and the nappy area. Typically it flares in the heat and settles as the skin cools, and it may come and go with the weather and activity through the day.

Who gets it

Anyone can get prickly heat given enough heat and sweating, but some people are more prone:

Babies and young children, whose sweat glands are still developing and who cannot easily cool themselves or shed layers – they overheat readily if over-dressed or wrapped too warmly.
People who sweat a lot or are physically active in the heat.
People who are overweight, where warm, moist skin folds trap sweat, or who are unwell or bedbound and lie against bedding for long periods.
People wearing heavy, tight or non-breathable clothing, or thick occlusive creams over large areas.
Newcomers to a tropical climate whose skin has not yet adjusted to constant heat and humidity – a common experience for those newly arrived in Singapore.

Causes and triggers

The single underlying cause is blocked sweat ducts with sweat trapped underneath. Anything that makes you sweat heavily, slows sweat from evaporating, or seals the skin can bring it on:

Hot, humid weather – sweat evaporates slowly when the air is already damp, so it lingers on and under the skin.
Heavy sweating from exercise, exertion or fever.
Tight, heavy or synthetic clothing that traps warmth and moisture against the skin.
Thick, greasy creams and ointments that sit on the skin and block the duct openings.
Prolonged lying down or anything that keeps a patch of skin warm, covered and unable to breathe.

Why it is common in Singapore

Singapore’s consistently hot, humid weather means people sweat heavily and the sweat evaporates slowly, so ducts block more easily. Add repeated swings from cold air-conditioned indoors to hot, sticky outdoors, tight or synthetic clothing, and vigorous activity, and heat rash becomes a frequent, if minor, nuisance for children and adults alike. Babies are especially prone because their sweat ducts are immature and they cannot easily cool themselves – so it helps to avoid over-dressing them, even when a well-meaning instinct is to wrap them up.

How it is recognised

Prickly heat is usually diagnosed just by looking at it and by the setting – a prickly, bumpy rash on sweaty, covered skin during hot weather that eases when you cool down. No tests are normally needed. A doctor may want to take a closer look if the rash is unusually widespread, keeps coming back, or could be something else, because several other itchy rashes can look similar in skin folds and warm areas. A GP or dermatologist can usually tell them apart on examination without special investigations.

Treatment and self-care

The heart of treatment is straightforward and needs very little from a pharmacy: cool the skin and reduce sweating, then let the skin dry and breathe. Most cases settle on their own once the skin cools down.

Cool down: move to a cooler, air-conditioned or well-ventilated place, and let the skin come back to a normal temperature.
Wash and dry gently: take a cool shower, then pat the skin dry rather than rubbing, and let affected areas air-dry before dressing.
Wear loose, light clothing: choose breathable cotton and avoid tight or synthetic fabrics that trap sweat and heat.
Keep the skin uncovered where you can: good airflow helps the ducts clear.
Avoid heavy creams and ointments on the rash, as thick, greasy products can further block sweat ducts; a light soothing lotion or a cool compress can ease the itch.
Ease off sweating triggers: limit strenuous activity in the heat until the rash settles, and keep up your fluids.
Try not to scratch: scratching breaks the skin and can let infection in. Keeping the skin cool is the most effective way to calm the itch.
For babies: remove excess layers, keep them in a cool room, use light bedding and light clothing, and do not bundle them up.

Preventing it in Singapore’s climate

Because heat rash is driven by heat and trapped sweat, prevention mirrors the treatment. Stay cool and well ventilated in hot, humid weather, and make use of fans and air-conditioning during the hottest part of the day. Wear loose, light, breathable clothing, and change out of sweat-soaked clothes after exercise or a hot commute. Avoid heavy, occlusive creams over large areas of skin, and dry skin folds gently after washing or sweating. For babies and young children, the key is not to overheat them – dress them lightly, keep their room cool and airy, and avoid over-wrapping, especially at night.

Complications

Prickly heat usually causes no lasting harm and clears without a trace. The main problem to watch for is skin infection, which can follow when the rash is scratched and the skin surface is broken – shown by increasing redness, swelling, pain, pus or fever. Rarely, a very widespread heat rash can interfere with the skin’s ability to sweat and cool the body, which matters most in prolonged heat. Keeping the skin cool and unbroken prevents both of these.

When to see a doctor

Heat rash is usually harmless, but see a doctor if:

the rash does not settle after a few days of cooling and drying, or keeps recurring;
there are signs of infection – increasing pain, spreading redness, swelling, pus, or fever;
you’re unsure it is heat rash, as several other itchy rashes (such as eczema, fungal infections in skin folds, or contact dermatitis) can look similar;
a baby is uncomfortable, feverish, overheating or generally unwell.

Separately, and more urgently, seek help straight away if – with or without a heat rash – someone shows signs of heat exhaustion or heat stroke, which is a different and potentially serious problem. Warning signs include feeling very hot with dizziness, nausea, headache and heavy sweating, and, more seriously, confusion, a very high body temperature, or collapse. Heat stroke is a medical emergency in the heat and needs immediate care. For a persistent or unclear rash, a dermatologist can confirm the diagnosis; a GP is a good first port of call, and HealthHub offers general local advice on coping with the heat.

Related skin & dermatology topics

Sources

NHS — Heat rash (prickly heat / miliaria): cause (blocked sweat ducts), symptoms, self-care (cool, loose clothing, avoid blocking skin), when to see a GP.
DermNet — Miliaria: types (crystallina, rubra), mechanism, management.
American Academy of Dermatology (AAD) — Heat rash: cooling, breathable clothing, babies.
HealthHub Singapore — heat-related skin and climate context (general local relevance).

General information only. This guide is general information about a skin condition and is not a diagnosis or personalised medical advice. See a doctor — a GP or a dermatologist — for assessment, tests and treatment. Have any new, changing, non-healing, bleeding or growing skin lesion or mole checked promptly, as this can be an early sign of skin cancer.

Prickly Heat (Heat Rash / Miliaria) in Singapore