What to expect from narrowband UVB phototherapy for sun allergy

Polymorphic light eruption can cause an itchy rash after sunlight exposure, often on areas that have not had recent sun exposure. A dermatologist may plan narrowband UVB before a period when symptoms commonly occur. The exposure is increased cautiously so the skin can adapt without provoking a significant burn. Protection habits remain necessary because phototherapy does not make all sunlight harmless and reactions can still occur.

Tell the clinic about medicines or products that make you more sensitive to light, and mention any history of cold sores or unusual light reactions. Attend at the planned intervals and avoid adding outdoor or tanning exposure around treatment without advice. Use shade, protective clothing, and sunscreen as recommended. Record when rash, itching, swelling, or blisters appear, including the exposed area and products used, so your clinician can distinguish expected adaptation from a flare.

Contact the clinic if redness is intense or persistent, or if blisters, marked swelling, or significant pain follow a session. Seek urgent help for breathing difficulty, facial or throat swelling, faintness, or a rapidly spreading reaction. Ask for review if the rash changes pattern, occurs without light exposure, or keeps returning despite the agreed prevention plan.

Ask when to start the course, how to protect treated and untreated skin, and which reaction means the next exposure should be delayed. Clarify whether your usual creams or medicines should be paused on treatment days.