Heat allergy rash: what should you know?

Sweat trapped beneath the skin can cause small prickly bumps, especially under clothing or in skin folds. Heat-triggered hives tend to be raised and itchy and may flare with exercise, hot showers, stress, or a warm environment. Eczema, contact dermatitis, and fungal infection can also worsen in heat, so a persistent or unusual pattern deserves assessment.

Move to a cooler place, loosen damp clothing, rinse with cool or lukewarm water, and pat the skin dry. Wear breathable clothing and take breaks from heat and exertion. Do not scratch or apply strongly scented products. Note the trigger, distribution, duration, and whether individual raised areas fade while new ones appear; this helps a clinician distinguish patterns.

Call emergency services for wheezing, trouble breathing, swelling of the lips or tongue, faintness, or widespread symptoms with feeling unwell. Arrange medical review if the rash is painful, infected-looking, recurrent, spreading despite cooling, or accompanied by fever.

Ask whether the appearance fits heat rash, hives, eczema, or another condition; which cooling or anti-itch options are suitable; and whether you need an action plan for exercise or hot weather.