Heat rash
Also called Prickly heat, miliaria
- Typical age
- Any age, common in babies
- Where
- neck, chest, armpits, diaper area, skin folds
- Fever
- no
- Itchy
- yes
- Contagious
- No
- Usually lasts
- 2–3 days once cooled
What it looks like
Tiny red or clear pinpoint bumps in areas that sweat or are covered, like the neck and chest.
On brown and black skin, redness may look purple, grey or darker than surrounding skin; texture (raised, rough, blistered) is often the better clue.
What causes it
Blocked sweat ducts from overheating or too many layers.
What helps at home
- Cool your child down: remove a layer, loosen clothes, move to a cooler room.
- A lukewarm bath and air-drying helps.
- Avoid thick creams that trap heat.
When to call about heat rash
Call 911 or go to the ER now
- Signs of heat exhaustion: very sleepy, vomiting, hot dry skin
- Rash that does not fade when you press a clear glass against it (possible petechiae or purpura)
- Baby under 3 months with a temperature of 100.4°F (38°C) or higher
Call your pediatrician today
- Not improving after 3 days
- Bumps fill with pus or skin looks infected
- Fever develops
General guidance based on AAP, NHS and CDC advice, not a diagnosis. If your gut says something is wrong, call your pediatrician or nurse line. You never need permission to seek care.
Questions parents ask
How long does heat rash last on a baby?
Usually 2 to 3 days once the skin is kept cool and dry.
Rashes often confused with heat rash
- Hand, foot and mouth disease · mouth, hands, feet
- Roseola · chest, back, tummy
- Diaper rash · diaper area
- Erythema toxicum · chest, face, arms