Toddler and Baby Heat Rash (Prickly Heat)

This page answers the following questions on toddler and baby heat rash, which is also known as miliaria or prickly heat.

Miliaria is common in newborn babies but can be seen in older infants and children as well. It is caused by the ducts from the sweat glands getting blocked so is more common in hot, humid environments.

What causes heat rash in toddlers and babies?

As its name suggests, heat rash is caused by the skin overheating. The ducts from the sweat glands get blocked. There are different types, (miliaria crystallina and miliaria rubra) depending on what layer of skin is involved (miliaria rubra occurs in deeper tissues).

Miliaria is also known as prickly heat.

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What does heat rash look like?

It usually affects skin that is covered by clothing. There are small raised red spots (which is usually deeper in the skin and known as miliaria rubra) or small blisters (which is usually more superficial and known as miliaria crystallina).

prickly heat toddlerMiliaria rubra
prickly heat babyMiliaria crystallina

The rash is itchy - which is why it's called prickly heat - it feels like prickles under the skin.

miliaria crystallinaClose Up
prickly heatFaint heat rash

The miliaria rubra rash can look similar to folliculitis (which is inflammation of the hair follicles) but in miliaria the hair follicles are not involved.

The photo of the faint rash is of a baby who is well in himself. It was a very hot day and he had just been undressed.

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Who gets heat rash?

It is common in babies but is also a rash that can occur in children. Newborn babies often have the miliaria crystallina type which is superficial and has small blisters.

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What is the treatment of heat rash?

The only treatment is cooling and avoidance of overheating. Give your child a cool bath and use light cotton clothing that is not too tight. Applying a cool (not cold) flannel to the area may provide instant relief.

In cases that take a bit longer to resolve, a topical steroid may be helpful.

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How long does the heat rash last?

It depends on what type of miliaria and how soon the skin is cooled. The rash of miliaria crystallina (the usual baby heat rash) can go in hours once the baby is cooled.

In miliaria rubra, which is deeper, the rash may last a couple of days and in severe cases, it can last weeks.

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  • Dershewitz R. Ambulatory Pediatric Care. Lippincourt-Raven. 1999


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Last reviewed 14 September 2011

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Dr Maud MD

Dr Maud MD (MBChB, FRACP, FRCPCH), a specialist pediatrician, provides health information and medical advice for parents of babies and toddlers. Read more about Dr Maud.

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