Skin rash caused by sweating: what helps?

What does heat rash look like?

Heat rash usually appears as clusters of small raised spots with itching, prickling or mild swelling. The spots look red on white skin, but can look grey or white and be less obvious on brown or black skin. Some contain fluid. Heat rash can appear anywhere and spread across the body, but it cannot spread to another person. The common itchy form often affects the upper body, neck and skin folds, particularly where clothing rubs. Another form produces tiny, clear blisters that resemble beads of sweat and break easily; these usually have no surrounding inflammation. Miliaria is the medical name for heat rash.35

Why does sweating cause a rash?

Sweat normally travels through tiny ducts to the skin's surface, where evaporation helps cool your body. When a duct becomes blocked, sweat backs up and causes inflammation inside the skin. Heavy sweating and a buildup of dead skin cells can contribute to blockage. Hot, humid weather, intense exercise, fever and tight clothing increase the risk. Heat rash also affects people on bed rest, especially on the back. Babies are more vulnerable because their sweat ducts are still developing. Some medicines, including beta blockers, clonidine and opioids, can increase sweat gland activity. Tell a clinician about your medicines if the rash keeps returning; do not stop medicines without their advice.256

What should you do when the rash starts?

1. 1Move somewhere cooler and pause activities that make you sweat heavily. An air conditioned room helps reduce sweating, even though it comes without a skincare label.
2. 2Remove wet or tight clothing. Leave the affected area uncovered where practical, or change into clean, loose cotton clothing that does not rub.
3. 3Wash gently with cool or lukewarm water, then pat dry. Do not scrub the rash or use perfumed shower gels.
4. 4Apply a cool, damp cloth to calm the prickling. Use it for up to 20 minutes; wrap an ice pack in a towel rather than placing it directly on your skin.
5. 5Tap or pat itchy skin instead of scratching. Keep nails clean, short and smooth to reduce damage if you scratch.

Should you use calamine, hydrocortisone or moisturizer?

Cooling comes first. Avoid covering heat rash with thick creams, ointments or powders that can block sweat from escaping. If itching is troublesome, a pharmacist can help choose a suitable treatment, such as calamine lotion, an antihistamine tablet or hydrocortisone cream. Children under 10 need a doctor's advice before using hydrocortisone for heat rash. Calamine can relieve discomfort, but it also dries the skin. If dryness becomes a problem, ask about a suitable emollient, a moisturizer that softens dry skin, rather than layering several products over the rash. There is no single application schedule for these treatments: follow the directions for the specific medicine and the pharmacist's advice. An unperfumed moisturizer is useful for dry, irritated itchy skin, but treating dryness is different from covering blocked sweat ducts. Avoid perfumed creams, soaps and deodorants on irritated skin. If the problem is dry patches rather than a short lived prickly rash, the cause needs a different assessment.2357

How long should heat rash take to clear?

Most heat rash resolves within a day or two after moving to a cooler environment, although it can take a few days. Cooling and reducing irritation are often enough without medicine. Continued sweating can irritate the rash, so limit sweaty exercise while it heals. Arrange a medical appointment if there is no improvement after a few days rather than repeatedly trying different creams.235

How can you stop it returning?

Schedule outdoor exercise for the coolest part of the day, or exercise indoors with air conditioning. Use fans and cool showers, and choose lightweight, loose cotton clothes in hot weather. Change out of sweaty workout clothes promptly and wash them before wearing them again. Blot sweat with a clean towel rather than rubbing it away. Sleep in a cool, ventilated room and avoid excessive clothing. A cooler bedroom and lighter bedding help reduce sweating, so the duvet does not need to take its winter job into summer. If heat and humidity are unavoidable at work, take cooling breaks where possible. Repeated episodes deserve a medical review, especially if keeping cool does not prevent them.1235

Could it be something other than heat rash?

A rash after sweating is not automatically heat rash. Folliculitis is inflammation from infected hair follicles: the bumps resemble pimples and tend to feel itchy and tender. Sweat mixed with skin oils and bacteria can also contribute to acne breakouts. Contact dermatitis is irritation or an allergic reaction after skin touches something. Fragrances, cosmetics, detergents and strong soaps are possible triggers. Tell a clinician about new products, workplace exposures and when the rash started. Heat and sweat can also trigger itching in neurodermatitis, an eczema condition involving persistent itchy patches and scratching. Those patches usually need prescription treatment, not cooling alone. If you already have a treatment plan, use medicines as directed. For diagnosed neurodermatitis, apply fragrance free moisturizer at least daily and after bathing, while skin is still damp. A cool compress for 10 to 15 minutes a few times daily can give temporary relief.146

When should you get medical help?

Contact a clinician if the rash is painful, intensely itchy, worsening or not improving after a few days. Warm, swollen skin, yellow or green fluid, red streaks, fever or chills can indicate infection. Blisters around the eyes, mouth or genitals also need medical assessment. For babies, avoid excessive layers and blankets, but keep loose fabric away from their face. Contact their clinician if the rash persists, keeps returning or worries you. During pregnancy, tell your doctor or midwife about itching, rather than assuming sweating explains it. Pregnancy itching sometimes has a liver related cause. Seek assessment too if itching is severe, widespread, keeps returning or affects daily life. Call emergency services for a sudden rash that spreads quickly, trouble breathing or facial swelling. These can be signs of a severe allergic reaction.2367