Heat rash
Heat rash appears when the ducts of the sweat glands become blocked and sweat cannot reach the surface of the skin.
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Medicines commonly prescribed for Heat rash
For informational purposes only. Always consult a doctor before using any medicine.
Dosage form: CREAM, 0.1% w/w betamethasone / 100 gActive substance: betamethasoneManufacturer: Industrial Farmaceutica Cantabria S.A.Prescription requiredDosage form: OINTMENT, 64 mg betamethasone dipropionate / 100 gActive substance: betamethasoneManufacturer: Organon Salud S.L.Prescription requiredDosage form: TOPICAL SOLUTION, 64 g betamethasone dipropionate / 100 gActive substance: betamethasoneManufacturer: Organon Salud S.L.Prescription required
Heat rash appears when the ducts of the sweat glands become blocked and sweat cannot reach the surface of the skin. Trapped underneath, it irritates the tissue and produces a fine rash that itches and prickles. It is uncomfortable but harmless: once the skin is properly cooled it clears by itself within a few days, and it does not spread to other people.
What it looks like
- small bumps or blisters in clusters;
- a prickly, itchy or faintly burning feeling;
- slight puffiness of the surrounding skin;
- on pale skin the rash looks reddish; on brown and black skin it may appear grey or whitish, and is sometimes easier to feel than to see.
It favours places where skin is poorly ventilated and rubs against clothing: the neck and the folds under the chin, chest and back, armpits, the inside of the elbow, under the breasts, the groin, and in babies the scalp as well.
What to do
There is really only one aim — stop the sweating in that area and let the skin cool. Everything else is secondary.
- move to a cooler room or sit in front of a fan;
- take off the extra layers and put on loose cotton;
- have a cool shower and let the skin air-dry rather than rubbing it with a towel;
- apply a cool, damp compress for 15–20 minutes;
- drink more fluid;
- use light bedding, and in hot weather as few layers as possible.
What does not help: greasy creams and ointments, which block the ducts further; occlusive dressings; scented shower gels; and scratching. Itching responds better to cold and to patting the skin.
A pharmacist may suggest calamine lotion or an antihistamine if the itching is troublesome. Hydrocortisone cream is used only on medical advice, and is not applied to children without asking first.
In babies
Heat rash is common in the first months of life: the sweat glands are still working immaturely and a baby is very easy to overdress. The rule of thumb for clothing is simple — one layer more than an adult in the same room, and no more. To check whether a baby is too warm, feel the neck and back rather than the hands and feet: those are cool almost all the time.
When to see a clinician
- the rash has not improved in 3–4 days despite cooling the skin;
- pus-filled spots, crusting or increasing tenderness appear — signs of added infection;
- there is a fever;
- the rash is spreading or itching severely;
- it is a baby and you are not sure this is heat rash;
- the child is listless and refusing food and drink.
Separately: a rash that does not fade when pressed with a clear glass, together with fever and a child who is becoming unwell, means seeking emergency help immediately. That is how meningococcal infection presents, and it is not heat rash.
How to stop it coming back
Heat rash returns if the conditions that caused it are still there: heat, humidity, tight synthetic clothing, overheating under a duvet, hard exercise with no chance to cool down. Loose clothing in natural fabrics, a cool bedroom, a shower after exertion and drying the skin folds properly all help.
Common questions
Is it catching? No. It is a reaction of the skin to overheating, not an infection.
Can I bath my baby? You should. A lukewarm bath helps; the only thing that matters is not rubbing the skin afterwards.
Does talcum powder help? It dries the skin, but applied thickly into folds it clumps and irritates. Cooling comes first.
Online consultation
In an online appointment a doctor can review photographs of the rash, help tell heat rash apart from other eruptions, advise on relieving the itch, and explain which signs mean an in-person examination is needed.
This article is for general information and does not replace a consultation with a doctor.
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Medically reviewed by
Reviewed on Jul 22, 2026
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