What should you know about a heat rash spot?

One spot can appear where clothing, a strap, hair, skin folds or exercise has held heat and moisture against the body. It may itch, prick, sting or feel tender. The surface can be skin-coloured, pink or red, and a tiny fluid-filled blister may develop. A single mark is not enough to identify the cause: an insect bite, contact irritation, follicle inflammation or another type of skin rash can look similar.

Take note of its exact position and timing. A spot that changes after cooling is different from one that becomes hot, swollen, increasingly painful or wet.

Cool the area with a damp cloth, then pat it dry. Remove tight or heat-trapping clothing and avoid scratching, squeezing or popping a blister. Keep the surrounding skin clean and dry. Do not layer several new products on the mark, since fragrance and heavy occlusive preparations may increase irritation. If itch persists, ask a pharmacist or clinician whether an emollient or topical corticosteroid is appropriate for that site.

Seek medical advice if the mark enlarges, new spots appear, or it fails to improve after the skin is kept cool and dry. Prompt assessment is sensible for pus, crusting, spreading redness, warmth, swelling, fever or significant pain. Urgent help is needed with breathing difficulty, facial swelling, faintness or a rapidly spreading blistering rash.

Ask what features distinguish heat rash from a bite or contact reaction, whether the site needs a medicine, and which warning changes should prompt a return visit.