Published: 29 July 2026
Tiny bumps after a hot night can look alarming. Heat rash in toddlers usually does no harm and clears within days. Cool your child gently and avoid products that trap more heat.
Heat rash is caused by blocked sweat ducts. Trapped sweat creates spots or tiny blisters. Its medical name is miliaria; the itchy form is miliaria rubra. This type of miliaria is also called prickly heat.
Babies and toddlers are particularly prone to it because their sweat ducts are still developing. Younger babies may be especially sensitive to overheating. Heat rash is not contagious, so your child cannot pass it to nursery friends. Team at our nurseries in London help children stay comfortable by adapting clothing, activities and indoor spaces during warmer weather.
Typical symptoms of heat rash include raised spots, prickling and mild swelling. NHS guidance says spots usually measure 2mm to 4mm; some contain fluid.
On white skin, the area often looks red or pink. On brown or black skin, it may appear grey or white. Check its texture as well as its colour.
Heat rash can develop anywhere, but it favours warm places where sweat and friction meet. Check the neck, upper chest, back, armpits, groin and skin folds, plus areas beneath a nappy, waistband or hat.
No checklist can diagnose every childhood rash. Heat rash symptoms usually follow sweating or overdressing, cluster on covered areas and start settling once the skin stays cool.
Eczema more often produces dry, rough patches and tends to recur. Hives form raised welts that can change shape or move around the body. Call 999 for breathing difficulty or swelling of the lips, mouth, throat or tongue.
If a rash does not fade when you press a clear glass firmly against it, seek urgent medical help. Do not wait for every typical sign or symptom to develop, particularly if your child seems unwell.
The direct cause is sweat trapped beneath blocked ducts. Hot weather, heated rooms, heavy bedding, close-fitting clothing, fever or vigorous play can trigger toddler heat rash.
Friction adds to the problem. A snug collar or nappy edge rubs damp skin, while tightly woven fabrics hold warm air against the body.
The main treatment for heat rash is keeping the skin cool. Most cases settle without medicine or additional treatment, so address the cause rather than covering the spots.
Move your child into the shade or a well-ventilated room. Remove unnecessary layers and change damp clothing or bedding. A cool bath can also help.
Pat the skin dry or let it air-dry. Hold a cool, damp cloth over the area for up to 20 minutes, but never apply ice directly.
Keep fingernails short and encourage patting rather than scratching. Scratching can break the skin and create an entry point for bacterial infection.
If your toddler remains uncomfortable, speak to a pharmacist. They may suggest calamine lotion or another suitable treatment. Children under 10 need a doctor’s advice before using hydrocortisone for heat rash.
Skip thick creams or fragranced lotions unless a healthcare professional advises otherwise. They can block ducts or irritate sensitive skin. Never try to dry the rash with heat or sunlight.
Take a clear photograph in natural light when you first notice the heat rash on the toddler. Note where it appeared, when it started and whether your child had been sweating, sleeping or wearing extra layers.
This gives you something concrete to compare over the next few days and can help a pharmacist or GP understand how the rash has changed. Avoid repeatedly touching or pressing the area while checking it.
Choose loose cotton clothing, ventilate bedrooms and check the back of your toddler’s neck or chest rather than judging their temperature from cool hands.
Plan active play for cooler parts of the day and offer regular drinks. Our guide to keeping children safe in the sun covers shade, clothing and sunscreen, while these summer activities for children include calmer ideas for warm days.
At night, use light bedding and recheck your child after they fall asleep because their temperature can change once they stop moving.
See a GP if the rash has not improved after a few days, keeps worsening, or you are worried about your baby or toddler. Seek medical advice sooner if the skin becomes increasingly painful, hot or swollen, or develops pus, spreading redness or crusting. These symptoms can signal infection.
A child with straightforward prickly heat should otherwise seem well. Get health advice for a fever, reduced drinking or urination, unusual sleepiness, or signs of serious illness. Confusion, fast breathing, a seizure or loss of consciousness are emergency warning signs.
It usually clears within a few days. If it persists or returns without an obvious heat trigger, ask your GP to check the diagnosis.
Timing offers the best clue. Heat rash follows sweating and improves with cooling. Eczema creates persistent dry or scaly patches, while an allergy can cause fast-changing hives or swelling. Seek help rather than relying on appearance if you are unsure.
Start with a cool, damp cloth. If itching continues, ask a pharmacist which age-appropriate treatment to use.
Heat rash is not infectious, so the rash alone does not require exclusion. Tell the nursery, provide loose spare clothing and explain what helps your child stay comfortable.
If your toddler has a fever or feels unwell, follow the setting’s illness policy.
Yes, particularly if scratching breaks the skin. Watch for increasing warmth, pain, swelling, pus or redness that spreads beyond the original area, and contact a healthcare professional if these symptoms appear.
Notice the pattern. If spots repeatedly form beneath a particular sleep suit, hat or buggy strap, change that one factor first. A small adjustment to fabric, fit or timing often prevents the next flare without overhauling your whole summer routine.
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