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Heat rash

6-minute read

Key facts

  • Heat rash happens when your sweat glands become blocked.
  • Heat rash can cause red spots or clear blisters that are itchy.
  • Heat rash is common in babies, and in people who are adjusting to warmer temperatures.
  • You can talk to your doctor about medications to help ease heat rash symptoms.
  • Heat rash usually goes away by itself, but it can last up to 3 weeks.

What is heat rash?

Heat rash is a harmless but very itchy skin rash. It is also called prickly heat, sweat rash or miliaria.

It happens when your body sweats more than usual. Heat rash is more common during the summer months and in hot climates.

What are the symptoms of heat rash?

Heat rash causes:

  • tiny red spots, clear blisters or lumps
  • an irritating itchy and prickling sensation
  • red skin

Heat rash occurs in places where sweat collects, such as your:

  • armpits
  • back
  • under your breasts
  • chest
  • groin
  • elbow creases
  • back of your knees
  • waist

In babies, heat rash often appears:

  • in skin folds
  • on their face
  • in the nappy area

CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.

What causes heat rash?

Heat rash happens when your sweat ducts become blocked or inflamed due to heat and high humidity.

It is common in newborn babies as their sweat glands haven’t developed properly yet. It can also happen in older children.

Heat rash usually improves quickly. However, it can take up to 3 weeks.

You are more likely to get heat rash if you:

  • are getting used to warmer temperatures
  • wear too many clothes in warmer temperatures
  • lie in bed for long periods of time, especially if you have a fever (high temperature)

When should I see my doctor?

See your doctor if your rash becomes infected, such as if:

  • the blisters fill with pus
  • you develop a fever
  • you have swollen lymph nodes (glands)

FIND A HEALTH SERVICE — The Service Finder can help you find doctors, pharmacies, hospitals and other health services.

ASK YOUR DOCTOR — Preparing for an appointment? Use the Question Builder for general tips on what to ask your GP or specialist.

How is heat rash diagnosed?

Your doctor will diagnose heat rash by looking at your rash. They may take a sample of fluid from inside your blisters to check for other conditions.

How is heat rash treated?

Heat rash normally goes away without treatment, after you cool down and stop sweating.

You can ask your doctor or pharmacist about any medicines that can reduce itching and inflammation. They may suggest:

  • calamine lotion
  • a steroid cream

You many need antibiotics if the area becomes infected.

A cool bath or shower may help soothe itching in the short-term, but do not shower or bathe excessively. This can reduce the natural oils that protect the skin and may make your rash worse.

How can I help my child with heat rash?

If your child has heat rash:

  • keep them cool and dry
  • change sweaty clothes and wet nappies regularly
  • dress them in cotton clothes
  • carefully dry in between their skin folds after bathing
  • put them to sleep in just a nappy
  • don’t use lots of blankets
  • avoid using a plastic mattress

You can help to cool them with a lukewarm bath. You can also press a cool — but not cold — damp cloth on their skin.

Can heat rash be prevented?

To prevent heat rash from developing or getting worse, there are things you can do.

Keep cool to avoid sweating. Try to avoid heat and humidity. Stay in air conditioning or near a fan, and make sure there is good ventilation.

Try to wear loose cotton clothing which can help prevent you overheating. Avoid fabrics which irritate your skin, like wool or scratchy fabrics.

Complications of heat rash

If your heat rash becomes infected, you may need antibiotics.

If you get heat rash repeatedly, this can prevent you from sweating properly, and can lead to heat exhaustion.

Resources and support

You can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: November 2023

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