Rash on the arms: what should you know?

Dryness and itch can occur with atopic dermatitis. A rash limited to an area exposed to a new product may reflect contact dermatitis. Sweating can trigger heat rash, while sharply outlined scale may fit psoriasis. A ring-shaped, enlarging patch can occur with ringworm. A new medicine can cause a drug rash, and widespread night-time itch with affected contacts can point toward scabies.

Look at both arms in good light and note the start date, recent products, outdoor exposure, illness, and medicines. These details help a clinician separate look-alike conditions.

Clean gently, moisturise after washing, and avoid hot water, vigorous exfoliation, and scratching. Wear breathable clothing and stop a newly introduced product if it is a plausible trigger. Photograph changes for comparison. Avoid borrowing prescription creams: treatment for eczema, fungal infection, or another rash is not interchangeable.

Seek medical advice when the rash persists, spreads, repeatedly returns, or causes significant itch or pain. Get urgent help for breathing difficulty, swelling, fever with rapid spread, extensive blistering, skin peeling, purple spots, or involvement of the eyes or mouth.

What features point to the cause? Could a product, medicine, or infection be involved? Which cleanser and moisturiser should I use, and what changes would mean I need an earlier review?