How long does heat rash last?

Why cooling matters

Heat rash, also called prickly heat or miliaria, happens when sweat glands or their ducts become blocked and sweat gets trapped beneath the skin. Hot, humid weather, intense exercise and tight clothing can contribute. Reducing sweating and letting air reach the skin addresses the cause. The useful changes are mostly to the room and clothing, a rare occasion when the bathroom shelf is not in charge.1

What to do while it clears

1. 1Move into a cooler environment and limit time in the heat. Reduce activity that makes you sweat heavily.
2. 2Change into loose, breathable clothing and remove unnecessary layers.
3. 3Soothe itchy skin with a cool, damp towel or a cool or lukewarm shower. Avoid long baths or showers.
4. 4Dry excess moisture from the skin and keep the area cool and dry.

Pat or tap itchy skin instead of scratching it, and keep nails short and smooth. Calamine lotion can soothe heat rash. A pharmacist can help choose an appropriate product if itching is troublesome. Avoid moisturizers on the rash: keeping skin cool and dry takes priority over the usual moisturizing routine. Perfumed soaps and deodorants can also aggravate itchy skin.345

What if a baby or child has heat rash?

Heat rash is more common in young children. Dress babies in lightweight, soft cotton clothing and keep them cool and dry. Cotton absorbs moisture and helps keep it away from the skin, making the clothing choice rather less elaborate than a skincare shopping list. If air conditioning is unavailable, position a fan far enough away to give your baby only a gentle breeze.67

Avoid powders, creams and ointments on a baby's heat rash. Baby powder does not improve or prevent it, and creams and ointments keep skin warmer and block pores. For children, remove extra clothing, use a cool, damp washcloth to remove sweat and body oils, and dry excess moisture after a lukewarm bath or shower. Childhood heat rash normally leaves no permanent skin damage and is not contagious.27

Can heat rash last for weeks?

A rash lasting weeks should be assessed rather than assumed to be ordinary heat rash. Continued sweating and skin blockage are relevant triggers, but a persistent itchy rash can have other causes, including eczema, hives or a fungal infection. Arrange a medical appointment if cooling and self care are not helping, the rash keeps returning, or itching affects daily life. For a child, call the pediatrician if the rash is not improving within a few days.124

When should you get medical help?

Contact a clinician for pus drainage or unusually warm skin. In children, fever, chills, pain, swelling, worsening redness or acting sick also need medical attention. A child with uncomplicated heat rash should otherwise act normally and should not have a fever. During pregnancy, have itching checked by a doctor or midwife rather than assuming heat is the cause.234

Seek immediate medical care for dizziness, nausea, vomiting or headache after heat exposure, especially with confusion or slurred speech. These can be signs of heat exhaustion or heat stroke, not just a skin rash. Move out of the heat and begin cooling while getting help.3