Does narrowband UVB phototherapy treat sun allergy?

Sun allergy is often used to describe polymorphic light eruption, an itchy rash that can follow sunlight exposure. A dermatologist may prescribe a carefully increasing course of narrowband UVB before a season or period when flares are expected. The controlled exposure aims to build tolerance in the treated skin, but the benefit can vary and may not cover every body area. It is a preventive strategy rather than permission to seek unprotected sun. The diagnosis should be checked because several rashes can worsen with light.

Discuss timing with a dermatologist, especially if your rash is new, severe, or appearing after medicines or workplace exposures. Follow the exact session plan and continue shade, protective clothing, and the sunscreen advice suited to your skin. Record when the rash appears, which areas are affected, and any new products or medicines. Tell the clinic if a session causes escalating redness, pain, or blistering. Avoid adding outdoor sun exposure to the prescribed light course.

Arrange medical review for a rash that persists, spreads beyond sun-exposed sites, or includes blisters, pus, fever, facial swelling, or breathing symptoms. Seek urgent care for breathing difficulty, swelling of the lips or tongue, faintness, or a rapidly worsening reaction. Contact the phototherapy service promptly after treatment if burning or blistering is more than mild.

Is polymorphic light eruption the likely diagnosis? When should a preventive course start? Which skin areas should be treated or protected? What should I do if a flare occurs during the course?