Sun allergy: recognising photosensitive skin reactions

Different photosensitive disorders can produce small bumps, plaques, redness or blisters on exposed skin. Some medicines and skin products also make sunlight more likely to cause a reaction.

Photosensitive eruptions tend to favour areas reached by sunlight, such as the face, neck, upper chest, forearms or backs of the hands, while covered skin may be spared. The reaction can itch and may recur after exposure.

Sunburn more often presents with tender redness after excess ultraviolet exposure and may later peel or blister. A sharp edge at a sleeve or strap, the delay before symptoms, and any new medicine, fragrance or topical product can help a clinician distinguish among causes.

Move out of direct sun, cool the skin gently and avoid further exposure while it is inflamed. Use shade, tightly woven clothing, a broad-brimmed hat and broad-spectrum sunscreen suitable for sensitive skin. Reapply sunscreen according to its label, especially after swimming or heavy sweating.

Review medicine leaflets for photosensitivity warnings, but do not stop prescribed treatment without speaking to the prescriber. Photograph the distribution and list recent medicines, fragrances and skincare products. Bland emollients may ease dryness; a clinician can decide whether an anti-inflammatory treatment is appropriate.

Seek urgent assessment for extensive blistering, severe swelling, eye involvement, confusion, faintness, vomiting, marked weakness or signs of dehydration. Call emergency services for breathing difficulty or rapidly increasing swelling of the lips, tongue or throat.

Arrange a medical appointment if the rash keeps returning, occurs after limited exposure, leaves scars, affects covered areas as well, or began after a medicine change. Persistent skin redness, scaling or pigment change also warrants evaluation.

Ask whether the pattern fits sunburn, a photosensitive eruption or a product-related reaction. Discuss medicines that can increase light sensitivity, suitable sunscreen ingredients, whether testing is useful and how to treat future flares safely.