Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
2 min synopsisUK scopeSources checked 27 Aug 2026Clinical review pending
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Severe phototoxic burn or collapse
Painful confluent erythema, extensive blistering, skin loss, eye pain or visual change, syncope, heat illness or systemic symptoms after a session exceeds an expected mild treatment reaction and may require burn, ophthalmic or acute medical care.
Action: Stop further exposure, cool and assess ABCDE, surface area, hydration and eye symptoms, contact the phototherapy service immediately and arrange emergency or specialist burn assessment when severe; record lamp, delivered dose, positioning, medicines and timing.
Synopsis
Select supervised narrowband UVB or PUVA appropriately, establish an individual starting dose, prevent burns and ocular or genital exposure, reconcile photosensitising medicines, and monitor cumulative ultraviolet harm and treatment benefit.
Phototherapy is calibrated medical ultraviolet exposure delivered by a trained unit; natural sunlight and commercial tanning beds cannot substitute for its wavelength, dosimetry or safety checks.
Narrowband UVB reduces cutaneous inflammation and is used for psoriasis, eczema, vitiligo and selected photodermatoses after diagnosis-specific assessment.
PUVA combines psoralen photosensitisation with UVA, penetrates more deeply and carries more nausea, ocular precautions, phototoxicity and cumulative skin-cancer burden.
Key red flags
Blistering, severe or persistent pain, extensive erythema, mucosal or eye symptoms, fever, collapse, suspected machine or dosing error, a new photosensitising medicine, a changing pigmented lesion, or treatment in a person with major skin-cancer or photosensitivity risk requires prompt withholding and specialist review.
Phototoxic burn
Confluent tender erythema, oedema, blistering or pain appearing hours to three days after treatment indicates excessive ultraviolet exposure.
Investigation priorities
01
Pre-treatment skin and risk assessmentFirst step
Confirm indication and identify photosensitivity, malignancy and practical contraindications.
Management branches
First-line course planningSelect wavelength and establish baseline
Topical treatment is insufficient and supervised phototherapy is an appropriate next option.
Confirm diagnosis, treatment goal, extent, prior therapies, skin-cancer and photosensitivity risk, medicines, pregnancy context and attendance feasibility.
Choose narrowband UVB, PUVA or another unit modality for the disease and obtain consent covering burns, eye and genital protection, photoageing, cancer risk and alternatives.
Key medicines
Oral psoralen for PUVATake the hospital-pharmacy supplied number of tablets based on height and weight at the exact unit-specified interval, usually 2 hours before UVA; never repeat a vomited or missed dose without phototherapy-unit instruction.
Bland water-based emollientUse regularly between sessions for dryness; on treatment days apply only the unit-approved non-SPF water-based product at the permitted interval, commonly at least 2 hours before or immediately after exposure.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.