Why do I get heat rash so easily?

Why do I get heat rash?

Sweat normally travels through tiny tubes called sweat ducts to reach your skin's surface and evaporate. When those tubes clog, sweat stays inside the skin and causes inflammation. Heavy sweating can soften dead skin cells, making them more likely to clog the ducts. Heat rash, also called miliaria or prickly heat, often forms beneath clothing or in skin folds where airflow is limited.13

What makes it happen more often?

• Hot, humid conditions and sudden exposure to a warmer climate increase the risk.
• Exercise, physical work, fever and hyperhidrosis, a condition that causes excessive sweating, increase sweat production.
• Tight clothing, heavy layers and coverings that do not let moisture escape keep sweat against the skin.
• Bed rest, especially on waterproof mattress covers, can leave the back hot and covered.
• Some medicines, including beta blockers, clonidine and opioids, can increase sweat gland activity.
• Babies have developing sweat ducts and less effective temperature control, making heat rash especially common.

Tight clothing keeps heat and moisture close to the skin, which is efficient packaging for exactly the wrong thing.2

Is the rash definitely heat rash?

Typical heat rash has small raised spots, an itchy or prickly feeling and sometimes mild swelling. Spots can look red on white skin or grey or white on brown or black skin. Heat rash is not contagious. Not every rash that appears in summer is heat rash: dermatitis, reactions to sunlight and other conditions can look similar, so repeated episodes are a reason to check the diagnosis.24

What should I do when it starts?

1. 1Move into a cooler, ventilated or air conditioned space and stop activities that make you sweat heavily.
2. 2Remove extra layers and wet clothing. Leave affected skin uncovered where practical, or wear clean, loose clothing.
3. 3Gently wash with cool or lukewarm water, then pat dry without scrubbing.
4. 4Apply a cool, damp cloth for relief. A wrapped ice pack is another option, for up to 20 minutes.
5. 5Pat or tap itchy skin instead of scratching, and avoid perfumed shower gels or creams.

Cooling and airing out the skin are the main treatment, a rare occasion when skincare asks for less shelf space. Avoid layering on oils, thick creams or ointments that can trap moisture and worsen heat rash. For persistent itching, ask a pharmacist about calamine, antihistamines or hydrocortisone. Children under 10 need a doctor's advice before hydrocortisone is used.145

How can I stop it coming back?

Use loose cotton clothing, lightweight bedding and a cool bedroom. Remove wet clothes and take cooling breaks during hot work or exercise. For children, avoid overdressing and too many blankets. Drinking fluids helps prevent dehydration, but reducing heat and trapped sweat is the main way to prevent heat rash.34567

How long should it last, and when should I get help?

Most heat rash settles within a few days after cooling the skin. See a doctor if it keeps returning, covers a large area or does not improve after a few days in a cool place. Pain, increasing warmth or swelling, pus, fever or chills need medical attention because infection is possible.245

Confusion, unusual behaviour or loss of consciousness in the heat requires emergency help. Heat rash is a mild heat illness, but these symptoms can signal heatstroke rather than a skin problem.26