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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.

Phototherapy safety

Dermatology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

RapidFull
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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.
  • A minimal erythema dose can establish UVB sensitivity, while a minimal phototoxic dose after psoralen helps select oral PUVA exposure; skin-type protocols are alternatives when testing is unsuitable.
  • Ask before every session about erythema, itch, illness, missed visits, new medicines, topical products, sun exposure and any change in clothing or jewellery coverage.
  • Eye protection must fit and remain in place during exposure; male genital shielding is used unless the prescribed protocol deliberately treats that site.
  • Oral psoralen is usually taken two hours before UVA; UVA-protective glasses are worn for at least 12 hours, including near windows, with longer advice for children or cataract risk.
  • Do not expose previously covered untanned skin to an escalated dose by changing underwear, hairstyle, jewellery or position part-way through a course.
  • A burn can peak one to three days after treatment, so dose escalation uses the previous delayed reaction rather than appearance immediately after leaving the cabinet.
  • Record cumulative sessions and ultraviolet dose, response, burns and skin-cancer history and stop a burdensome or ineffective course instead of converting it into routine maintenance.

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.

  1. Confirm diagnosis, treatment goal, extent, prior therapies, skin-cancer and photosensitivity risk, medicines, pregnancy context and attendance feasibility.
  2. 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.
  3. Perform MED, MPD or an approved phenotype-based start, document shielding and provide written pre-session product and medication instructions.

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.Causes nausea, prolonged UVA sensitivity and ocular risk. Wear tested UVA-protective glasses for at least 12 hours, protect from daylight until day's end, review pregnancy and liver factors and avoid unsupervised additional UVA.
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.Oily, perfumed or unapproved products can block or intensify exposure and produce burns or patchy pigmentation. All emollient residue on fabrics increases fire severity.
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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

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.

  • BAD narrowband UVB phototherapyMED testing, session process, protection, burns, medicines and cumulative risk.
  • BAD oral PUVA phototherapyPsoralen timing, MPD testing, eyewear, daylight protection, adverse effects and long-term risk.
  • NICE psoriasis recommendationsNarrowband-UVB indications, frequency, response, relapse and treatment-sequencing principles.
  • NHS sunburnRecognition and first aid for minor ultraviolet injury and urgent assessment thresholds.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom