Heat rash

Summary

• Heat rash is a skin rash which appears when some children are very hot and become over-heated.
• It is most noticeable in folds in the skin, the chest and back and other parts of the body where clothing fits snugly
• Heat rash is not a serious condition

Alternative names

Miliaria or Prickly heat.

Definition

Heat rash is a skin rash which appears as a result of a child being very hot – in fact he or she may be over-heated.

Heat rash consists of small slightly raised, reddish-pink pimples that may appear when a child overheats in hot  and especially humid weather. It is most noticeable in folds in the skin and on parts of the body where clothing or nappies fit snugly, such as the chest, back, stomach, neck, genital area and buttocks. It may also spread across the head and forehead if the child is wearing a hat.

Cause

Heat rash seems to  appear when a child is sweating a lot. It is possible that there is some sort of irritation set up on the skin when the child sweats so much that the pores of the skin may become blocked and the sweat cannot be released as fast as it builds up.

Clothing that is tight fitting, clothing made of synthetic fibres or thick, warm clothing can trap sweat and contribute to the rash. Heat rash can also occur if the child has a high fever and is sweating heavily.

Prevention

Keep your child comfortably cool and avoid dressing him or her in tight-fitting clothing in hot weather. Some people believe that natural fabrics such as cotton allow easier movement of air across the skin and cause less sweating than artificial fibres.

 If it is very hot, make sure that your child plays inside or in the shade. Give him or her plenty of liquids to prevent dehydration.

Corn starch or talcum powder in skin creases can also help to prevent heat rash.

Treatment

Start by cooling your child down. Loosen or remove tight clothing and move him or her into a cool, shady place. Cool the area affected by the rash with cotton clothes soaked in cool water. A tepid bath can also help. Let the air dry the skin as much as possible and avoid using towels, as the rubbing can irritate the skin further.

Avoid ointments, creams or lotions that may prevent normal heat loss and increase sweating that may worsen the situation.

Heat rash is not a serious condition and the child will get better without any special treatment in most cases.

There may be some mild peeling of the affected skin area as the rash heals and disappears.

When to call the doctor

Call your doctor if your child has a fever which does not respond to medication or other cooling techniques.

If the rash does not disappear in three to four days, take your child to the doctor to check the diagnosis.

Previously reviewed by Prof H.F. Jordaan

Reviewed by Prof E Weinberg, Emeritus Professor of Paediatrics, May 2011