Heat rash, also called prickly heat or miliaria, develops when blocked sweat ducts trap sweat beneath the skin. It often affects covered areas and skin folds, where airflow is limited. Heat rash care is mostly about cooling and airflow, which gives the bathroom shelf an unusually small role.1

What should you do first?

  1. 1Move to a cooler or air conditioned room. Pause exercise or other activities that make you sweat.
  2. 2Remove wet clothing and uncover the affected skin where possible.
  3. 3Gently wash with cool or lukewarm water, then pat dry. Do not scrub or use excessive soap.
  4. 4Leave the area uncovered or wear clean, loose cotton clothing that does not rub against the rash.
  5. 5Apply a cool, damp washcloth whenever the prickly feeling needs soothing. A cool bath or shower can also help.
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Pat or tap itchy skin instead of scratching, and keep your nails short, clean and smooth. Scratching can break the skin and lead to infection. Avoid perfumed soaps, deodorants and moisturizers on the itchy area; these are general measures for easing irritated, itchy skin.13

Should you use a cream or calamine?

Start with cooling rather than covering the rash in products. Creams, ointments and powders that block pores can trap sweat and make heat rash worse. If itching is intense, ask a pharmacist or clinician about a suitable treatment before applying it. Calamine lotion can relieve discomfort, but it is drying; if dryness develops, ask whether an emollient, a moisturizing treatment, is appropriate.12

Hydrocortisone is a steroid medicine that reduces itching and inflammation, and skin formulations can be used for heat rash. Ask a pharmacist or clinician which formulation is suitable and how to use it, rather than choosing a steroid strength or schedule yourself.4

How long does heat rash take to clear?

Most cases settle within a day or two after moving to a cooler environment, though clearing can take a few days. Reduce heat and humidity throughout recovery, not just while applying a cool cloth. Sleep in a cool, ventilated room and avoid excessive clothing. A cooler bedroom belongs in the plan, even if it comes without skincare packaging.2

What if a baby or child has heat rash?

Babies and young children get heat rash more often than adults. Move your child somewhere cool to stop the sweating; the rash usually clears on its own within a few days and is not contagious. Avoid excess layers or blankets, and keep loose fabric away from a baby's face. Call your pediatrician if the rash remains after a few days or keeps returning.15

When should you get medical help?

See a clinician if the rash is not improving after a few days, is painful or intensely itchy, or you are unsure heat caused it. Get it checked for fever, chills, swollen or warm skin, yellow or green fluid, or red streaks. Tell the clinician about new medicines or skin products. During pregnancy, contact your doctor or midwife about itching rather than assuming it is heat rash.136

Get immediate medical help for a sudden rash that spreads quickly, trouble breathing or facial swelling. After heat exposure, confusion, dizziness, nausea or a rapid, strong pulse can signal heat stroke and need immediate help. Heavy sweating with rapid breathing and a fast, weak pulse can signal heat exhaustion, which can progress to heat stroke.67

Where this answer comes from

  1. 1Heat Rash Prickly Heat (Sweat Rash) Symptoms & Treatmentmy.clevelandclinic.org
  2. 2Heat rash (Miliaria): Images, Causes, and Treatmentdermnetnz.org
  3. 3Itchy skinnhs.uk
  4. 4Hydrocortisone: a steroid used to treat many health conditionsnhs.uk
  5. 5What are those bumps on my child's skin?aad.org
  6. 6Rash Evaluation: MedlinePlus Medical Testmedlineplus.gov
  7. 7Heat Illness: MedlinePlusmedlineplus.gov