Heat rash under the armpit

The armpit is a warm fold where sweat can remain against the skin. Arm movement, close clothing, shaving, deodorant, and damp fabric can add friction or irritation. Heat rash may appear as prickling, itch, small bumps, or red skin. However, a painful lump, ring-shaped rash, strong odour, scaling, or drainage may suggest a different problem and should not be self-labelled.

Rinse gently and pat the fold completely dry. Wear a loose top, change sweaty clothing, and give the area airflow when practical. Pause shaving and fragranced deodorant until the skin recovers. Avoid rubbing, adhesive coverings, and thick occlusive creams over moist bumps. If dryness remains after the area is calm, ask about a light emollient; see Emollient Therapy.

Do not use a steroid cream in the armpit without advice: folded skin can absorb medicines differently, and an incorrect product may worsen an infection or irritant reaction. See Topical Corticosteroids for background.

Arrange an examination if the rash persists, returns frequently, extends beyond the fold, or causes marked pain. Seek prompt care for warmth, swelling, pus, open skin, fever, a rapidly enlarging area, or red streaking. A clinician can distinguish heat rash from infection, contact dermatitis, fungal irritation, or an inflamed follicle.

Tell the clinician about deodorants, shaving, exercise, new clothing, sweating, and any lumps. Ask what to apply, when to restart deodorant, and how to protect the fold during hot weather.