When is narrowband UVB phototherapy recommended for sun allergy?

Sun allergy, often called polymorphic light eruption, causes an itchy rash after light exposure in people who are sensitive to it. A supervised course of narrowband UVB can gradually expose the skin to controlled light and may reduce the tendency to flare. This approach is usually considered before a season or expected period of outdoor exposure, not during an unexplained severe rash. The diagnosis matters because several medicines and skin conditions can cause light-sensitive eruptions that need different care.

Bring a list of medicines, supplements and skincare products to the appointment, including anything bought without a prescription. Follow the clinic's exposure schedule exactly and do not add outdoor tanning or extra lamp sessions. Continue shade, protective clothing and a broad-spectrum sunscreen as advised; phototherapy is not a reason to stop protection. Report excessive redness, burning, blisters or a rash that lasts longer than expected. Keep photographs or notes about timing, body areas and triggers to help the clinician adjust the plan.

Arrange prompt review if the eruption spreads quickly, involves the eyes or mouth, becomes painful, blisters or leaves signs of infection. Seek urgent care for breathing difficulty, facial swelling, faintness or a rapidly worsening reaction after a medicine or light exposure. A rash that appears without a clear light trigger also deserves reassessment.

Ask whether the pattern fits sun allergy, when to begin the course, how long protection should continue, and how you will know whether the plan is helping. Ask which medicines should be checked before each session and what to do after a missed appointment.