Heat rash and infection: signs to watch for

Heat rash forms when sweat ducts become blocked in hot, humid conditions. Small itchy bumps and mild redness fit [Heat Rash](/conditions/heat-rash/). Scratching, rubbing or moisture can damage the skin barrier, allowing bacteria to multiply. Increasing tenderness, warmth, swelling, yellow drainage, crusting or a bad smell is more concerning than uncomplicated [Skin Bumps](/symptoms/skin-bumps/) or [Skin Rash](/symptoms/skin-rash/).

Cool the skin, wash gently and pat it dry. Keep nails short and avoid scratching, tight clothing and shared towels. Do not squeeze bumps or apply leftover antibiotics, steroid combinations or harsh antiseptics. A bland moisturiser may support a dry, intact skin barrier; see [Emollient Therapy](/treatments/medical-dermatology/emollient-therapy/) for general guidance. A clinician should decide whether infection needs prescription treatment; [Topical Corticosteroids](/treatments/medical-dermatology/topical-corticosteroids/) are not a substitute for assessment.

Seek same-day medical advice for spreading redness, increasing pain, warmth, swelling, pus, open sores or red streaking. Get urgent help for fever, chills, marked weakness, facial swelling, or rapidly worsening symptoms. Infants, older adults and people with reduced immunity should be assessed sooner when infection is suspected.

Ask whether the skin is infected, whether a swab or prescription treatment is needed, and which products should be stopped. Describe the speed of change, drainage, fever, scratching and any medical conditions that affect healing.