Skin allergies due to sun: what to know

A sun allergy is a reaction that develops on exposed skin after sunlight, commonly on the arms, chest, or neck. Polymorphic light eruption may appear as small raised spots, patches, or fluid-filled blisters, and the pattern can differ between people. It may occur after the first strong sun exposure of a season. A rash limited to exposed areas supports sun sensitivity, but medicines, fragrances, or another skin condition can create similar changes. A clinician may ask when the rash started, which areas were exposed, and what products or medicines were used.

Move out of direct sunlight when symptoms begin and cover the affected area with lightweight clothing. Use broad-spectrum sunscreen as directed, reapply after sweating or swimming, and avoid deliberately testing the rash with more sun. Keep the skin cool, use a bland moisturiser, and avoid scratching. A clinician may recommend a short course of a topical corticosteroid for inflammation; do not use one on the face or large areas without instructions. Recurrent cases may be assessed for supervised narrowband UVB phototherapy, which can help the skin adapt before periods of expected exposure.

Seek urgent help for swelling of the lips, tongue, or throat, trouble breathing, faintness, or a rapidly worsening reaction. Arrange prompt medical review if the rash is painful, widespread, infected-looking, associated with fever, or affecting the eyes. Book a dermatology assessment when episodes keep returning, leave marks, begin after a new medicine, or occur on covered skin as well as sun-exposed skin.

Ask whether the pattern fits polymorphic light eruption, whether a medicine or product could be contributing, and which sunscreen and topical treatment suit your skin. If episodes recur, ask whether testing or preventive phototherapy is appropriate.