Heat pimples on arms: what to know

Small red or skin-coloured bumps that itch after sweating may fit heat-related irritation. Pus-filled, tender or uniformly follicle-centred bumps can point toward folliculitis; recurring clogged spots may fit acne. Shaving, tight sleeves, backpacks and thick products can increase rubbing or trap sweat. A clinician can distinguish these from eczema or an allergic reaction by examining the pattern, surface and timing.

Heat pimples are a symptom pattern, not a diagnosis. See the general guide to [Pimples](/symptoms/pimples/) and learn how [Folliculitis](/conditions/folliculitis/) can affect hair follicles.

Move to a cooler setting, rinse sweat away with lukewarm water and pat dry. Wear loose, breathable sleeves and change damp clothing promptly. Avoid scrubbing, picking, heavy oils and fragranced products on the area. Keep straps and rough fabrics from rubbing the bumps. If the spots began after a new product, stop it while the skin settles. A dermatologist may recommend treatment based on whether the pattern is acne, folliculitis or heat irritation; [LED Light Therapy](/treatments/laser-and-energy/led-light-therapy/) is one treatment topic to discuss, not a self-diagnosis.

Arrange an assessment if the bumps are painful, spreading, draining pus, leaving dark marks or scars, or returning despite cooling and gentle care. Seek prompt help for rapidly worsening redness, warmth, swelling, fever, facial swelling or breathing difficulty. A rash that follows a medicine or spreads beyond the areas exposed to heat also needs clinical review.

Ask whether the pattern is heat rash, acne or folliculitis; whether shaving, clothing or a product is contributing; and which cleanser or treatment suits your skin. Mention when it started, whether it itches or hurts, and any new medicines or products.