Deep heat rash: what to know

Heat rash, also called miliaria or prickly heat, can develop when sweat cannot reach the surface normally. In a deeper form, inflammation and fluid build up below the most superficial layer, so bumps may feel firm, swollen, or sore. Areas covered by tight clothing, skin folds, or equipment are common locations. Symptoms can include itching, stinging, redness, and small bumps, but a similar-looking rash may have another cause. See [Heat Rash](/conditions/heat-rash/) for the broader condition.

Hot weather, exercise, fever, occlusive products, and prolonged sweating can all contribute. The rash is not a sign that the skin is dirty. Scratching can break the skin and allow infection, so cooling and reducing friction are useful early steps.

Move to a cool environment, wear loose breathable clothing, and wash gently with lukewarm water. Pat dry rather than rubbing, take breaks from heat and exercise, and avoid heavy oils or fragranced products over the affected area. A plain moisturiser may help once the skin is no longer hot and sweaty; [Emollient Therapy](/treatments/medical-dermatology/emollient-therapy/) explains moisturising support. A clinician may recommend a short course of [Topical Corticosteroids](/treatments/medical-dermatology/topical-corticosteroids/) for selected inflamed cases. Do not use steroid cream on broken or infected skin without advice.

Seek medical advice if the rash does not start settling after cooling, keeps returning, spreads widely, or becomes painful rather than itchy. Fever, pus, increasing warmth, red streaks, or feeling unwell can signal infection and needs prompt review. Get urgent help for breathing difficulty, swelling of the lips or face, faintness, or a rapidly spreading rash. A rash that looks unusual or involves an infant should also be assessed.

Ask whether the bumps fit heat rash or another condition, whether any product or medicine is worsening blockage, and which cleanser or moisturiser is suitable. Clarify how long to use an anti-inflammatory cream, how to prevent recurrence in hot weather, and which changes should prompt a review.