Causes of heat rash or prickly heat

Heat rash or prickly heat happens because your child’s sweat glands aren’t fully developed. They can get blocked if she gets too hot. When this happens, sweat can get trapped under the skin and form small lumps or blisters.

This is why newborn babies often get heat rash in summer or in hot, humid climates. It might also appear during a fever, or if your child is overdressed.

Heat rash is common in babies, but can also happen in older children.

Symptoms of heat rash or prickly heat

Very small pinkish-red or clear blisters appear over your child’s face, neck and in the skin folds, especially in the nappy area.

If these blisters are infected, they might fill up with pus.

When to see your doctor about heat rash

Take your child to the GP if:

  • the blisters fill up with yellow or green pus – this means they’re likely to be infected and need treatment
  • the rash lasts more than three days
  • in addition to having a rash, your baby is generally unwell, has a fever or isn’t feeding well.
Not every rash is just a heat rash. Check with your GP if you’re in any doubt or are worried.

Treatment for heat rash or prickly heat

You can usually treat heat rash or prickly heat by making sure your child stays cool and avoids getting sweaty. You can do this by using air-conditioning if you live in a hot climate and avoiding too many layers when you dress your child. Dressing him in light cotton clothing is also a good idea.

If you wrap your baby, make sure she doesn’t get too warm.

To help your child feel more comfortable, you can give him a bath in lukewarm water. It’s best to avoid soap, because this can irritate your child’s skin. You can also put calamine lotion on the rash.

The rash should disappear in 2-3 days, but can take longer than this.

If your child is scratching at the blisters, speak to your GP or child and family health nurse about creams that might help.

Prevention of heat rash or prickly heat

Try to dress your child for the weather conditions and avoid too many layers of clothing.

Dry your baby’s skin folds after each bath.