Sun allergy on the arms: what to know

Sun allergy, also called polymorphic light eruption, commonly appears on exposed skin such as the arms as itchy red spots, small bumps, or patches. It may occur after stronger or longer sun exposure and can recur with later exposure. Sun sensitivity is a broader symptom and can also relate to medicines or other skin conditions, so a rash on sun-exposed skin is not automatically an allergy. Photos, timing, and whether covered skin is spared can help a clinician assess the pattern.

Cover the arms with closely woven clothing, seek shade, and use a broad-spectrum sunscreen that your skin tolerates. Reapply it as directed on the product label, especially after swimming or sweating. Cool compresses and a bland moisturiser may ease irritation. Avoid deliberately tanning the rash and pause new fragrances or topical products until the skin settles. A clinician may recommend a short course of topical corticosteroids for an active flare. Recurrent or difficult cases may be considered for narrowband UVB phototherapy under supervised care.

Seek urgent help if the rash comes with facial swelling, breathing difficulty, faintness, blistering, widespread skin peeling, or mouth or eye sores. Arrange assessment for a rash that spreads beyond exposed areas, leaves unusual bruising or pigment change, becomes painful or infected, follows a new medicine, or returns despite careful sun protection. A clinician should review persistent or recurrent arm eruptions.

Ask whether the pattern fits sun allergy or another cause of sun sensitivity, whether a medicine could be contributing, which sunscreen and clothing are suitable, and whether topical corticosteroids or supervised narrowband UVB phototherapy are appropriate.