What should you know about severe allergy to the sun?

Polymorphic light eruption is a sun-triggered skin reaction that may appear hours or days after exposure. It can cause clusters of red bumps, patches, blisters, or intense itch on areas that are newly exposed, such as the arms, chest, or neck. The rash is not the same as ordinary sunburn, and medicines or another light-sensitive condition can produce similar findings.

A clinician may review the timing, distribution, products used on the skin, and medicines. Take photographs when the rash is visible, especially if it fades before the appointment.

Cover exposed skin with closely woven clothing, use shade, and apply broad-spectrum sunscreen as advised. Increase exposure gradually only under a clinician's plan. Avoid tanning equipment and check whether a new medicine or fragranced product could be contributing; do not stop prescribed medicine without advice.

Cool compresses and bland moisturiser may soothe irritation. A clinician may prescribe a topical corticosteroid for inflamed areas. Repeated or difficult flares can prompt discussion of specialist options such as narrowband UVB phototherapy.

Arrange prompt assessment for widespread blistering, severe pain, facial swelling, fever, eye involvement, skin peeling, breathing difficulty, or a rash that follows a new medicine. Emergency help is needed for swelling of the lips or tongue, faintness, or trouble breathing. A persistent or repeatedly severe reaction also deserves dermatology review.

Ask whether the pattern fits polymorphic light eruption, whether any medicine or skincare product increases light sensitivity, which sunscreen and clothing are suitable, and whether testing or preventive treatment is appropriate.