How to treat heat rash

What causes heat rash?

Heat rash, also called prickly heat or miliaria, develops when sweat ducts become blocked or inflamed. Hot, humid weather, intense exercise, tight clothing and fever can contribute. Anyone can get heat rash, but newborns are particularly vulnerable because their sweat ducts are immature. Being confined to bed can also increase the risk, especially when waterproof mattress coverings trap heat and moisture.2

The common prickly form causes small, itchy bumps, often in skin folds or places where clothing rubs. A milder form produces tiny, clear blisters that resemble beads of sweat. Appearance alone cannot settle the cause: fungal infections, acne and inflammation around hair follicles can resemble heat rash.2

How do you treat heat rash at home?

1. 1Move into a cooler room, preferably with air conditioning.
2. 2Remove clothing covering the rash.
3. 3Gently wash the area with cool or lukewarm water, then pat it dry without scrubbing.
4. 4Leave the area uncovered or put on clean, loose clothing that does not rub.
5. 5Apply a cool, damp washcloth as needed to ease the prickly feeling.
6. 6Pause exercise and other activities that cause heavy sweating until the rash has cleared.

Avoid excessive soap and irritating products, because the bathroom routine does not need a supporting cast. Change out of wet clothing and keep your bedroom cool and ventilated.2

What helps the itching?

General itch care can help you leave the rash alone: pat or tap the skin instead of scratching, and keep your nails clean, short and smooth. Use cool or lukewarm baths or showers, but avoid long soaks. Skip perfumed soaps, deodorants and moisturisers on itchy skin. Choose loose cotton clothing rather than tight clothes or wool, and use laundry detergent intended for sensitive skin.3

If itching remains troublesome, tell a pharmacist where the rash is and whether you have other symptoms. Antihistamines help some causes of itching, so they are not an automatic choice for every itchy rash. A pharmacist can help decide whether a medicine is appropriate or whether you need a doctor.3

Should you use cream, calamine or hydrocortisone?

Avoid creams, ointments and powders that block pores and trap sweat. If itching is intense, ask a pharmacist or clinician before applying a treatment such as calamine.1

Calamine can relieve discomfort, but it is drying; an emollient, a moisturising treatment, is sometimes needed alongside it. Mild steroid treatments are another option when heat rash needs medical care. An infected rash needs assessment and can require treatment for bacteria rather than another soothing lotion.2

Hydrocortisone is a corticosteroid medicine that reduces inflammation, including itching and swelling. Skin creams, ointments and lotions containing hydrocortisone are used for heat rash. The form matters: hydrocortisone tablets, injections and products intended for other body areas have different uses. Ask a pharmacist which skin treatment is suitable and follow that product's directions.14

How long does heat rash take to clear?

Many cases resolve within a day or two after moving to a cooler environment. Cooling and reducing sweating are the main treatment; medicine is not always necessary. See a clinician if the rash has not improved after a few days, is painful or causes intense itching.12

How do you treat heat rash in babies and children?

The same cooling, gentle washing and airing steps apply to children. Avoid too many clothing layers or blankets, and keep loose fabric away from a baby's face. Call your child's clinician if heat rashes keep returning or last longer than a few days. Severe cases sometimes need a prescribed treatment for itching or inflammation.1

When should you get medical help?

Contact a clinician if you or your child has:

• Severe pain or constant itching.
• Fever, warmth, yellow or green fluid, or red streaks around the rash.
• Blisters, especially around the eyes, mouth or genitals.
• A rash that persists despite home treatment.

Seek immediate medical attention for a sudden rash that spreads quickly, trouble breathing or facial swelling. These can be signs of a severe allergic reaction, not a rash to manage with cooling alone.5

Tell your clinician immediately if fever and a rash develop after taking a medicine, especially a new one. Medication reactions can appear within hours, days or even weeks.6

If you are pregnant and have itching, contact your doctor or midwife rather than assuming heat is the cause. Pregnancy itching sometimes comes from a liver condition called intrahepatic cholestasis of pregnancy.3

Watch for overheating beyond the rash

Heat rash is skin irritation from excessive sweating, but prolonged heat exposure can also cause heat exhaustion or heat stroke. Heavy sweating, rapid breathing and a fast, weak pulse are signs of heat exhaustion. Confusion, dizziness, nausea, dry skin or a rapid, strong pulse can signal heat stroke and need immediate medical help. Young children, older adults and people who are ill are especially vulnerable to heat illness.7

How can you stop heat rash returning?

Reduce heat and humidity where possible, avoid excessive clothing and choose breathable fabrics, because a dress code should not double as insulation. Use a cool, ventilated bedroom and change out of wet clothes. If itching keeps returning, affects daily life or becomes widespread, arrange a medical assessment rather than repeatedly treating it as heat rash.23