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Purpose and principlesIndications, selection and cautionsAssessment before treatmentTreatment approachRegimens, contraindications and interactionsComplications, monitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Phototherapy and systemic treatment principles

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

RapidFull
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Time-critical presentation

Generalised pustular psoriasis, erythroderma or systemic deterioration needs immediate same-day specialist treatment; routine outpatient phototherapy or slow systemic escalation is not an emergency substitute.

Purpose and principles

Select and sequence specialist psoriasis treatment beyond topicals, obtain informed consent, prevent phototherapy and medicine harm, and monitor response using skin, joint and life-impact outcomes.

Treatment beyond topicals is justified by combined severity and impact rather than a single score. Extensive disease is one route, but severe nail or palmoplantar impairment and major distress can also meet conventional systemic criteria.

Phototherapy and systemic medicines trade greater reach for greater monitoring. Choice should incorporate phenotype, arthritis, comorbidity, infection, previous treatment, conception plans, cumulative ultraviolet exposure, travel burden and the person's goals.

Specialist prescribing does not remove primary-care responsibility for reconciliation and warning symptoms. Every plan needs one monitoring owner, exact dose and day, baseline screen, review interval, response threshold and action for abnormal results.

Key points

  • NICE offers narrowband UVB to plaque or guttate psoriasis not controlled with topical treatment alone; two or three sessions weekly are options, with faster response commonly achieved at three.
  • Phototherapy is prescribed treatment, not advice to sunbathe: consent covers burns, photosensitivity, photoageing, cumulative skin-cancer risk, attendance and eye or genital protection where required.
  • Do not use phototherapy routinely as maintenance; change strategy after poor tolerance, inadequate response, rapid relapse beyond half of baseline within three months, impractical access or especially high skin-cancer risk.
  • NICE systemic eligibility requires failed topical control plus important physical, psychological or social impact and extensive, functionally severe local, or phototherapy-resistant or unsuitable disease.
  • Methotrexate is NICE first-choice conventional systemic treatment for most eligible psoriasis; it is taken once weekly, never daily, with one named day and toxicity monitoring.
  • Ciclosporin is NICE first-choice when rapid or short-term control is needed, for palmoplantar pustulosis, or around conception when conventional systemic treatment cannot be avoided.

Indications, selection and cautions

Phototherapy candidate

Plaque or guttate disease remains uncontrolled after correctly used topicals, and the person can attend a supervised unit and consent after photosensitivity and skin-cancer assessment.

Systemic-treatment candidate

Topicals do not control psoriasis, life impact is significant, and disease is extensive, functionally severe at a local site, or phototherapy has failed, is unsuitable or relapses rapidly.

Unstable diseaseRed flag

Generalised pustulation, erythroderma, fever, malaise, fluid loss or physiological deterioration bypasses routine outpatient sequencing and needs same-day specialist treatment.

Methotrexate toxicityRed flag

Oral ulceration, sore throat, fever, bruising, bleeding, new cough or breathlessness may signal serious marrow, infection or pulmonary toxicity; verify the dosing day and stop-seek-advice plan.

Phototherapy injuryRed flag

Marked erythema, pain, blistering or eye symptoms after ultraviolet exposure requires prompt contact with the phototherapy unit and dose review before another session.

Joint-domain mismatch

A skin-effective treatment may not control axial or peripheral arthritis. Active joints, dactylitis or enthesitis require rheumatology coordination when selecting a systemic class.

Red flags requiring action

  • Fever, diffuse pustules, extensive tender inflammation, haemodynamic change or reduced urine output requires acute specialist assessment before routine treatment selection.

Assessment before treatment

  1. 01
    First-line baseline severity and impactFirst stepFirst line
    Why
    Confirm treatment eligibility and provide a comparator for response across skin, high-impact sites and quality of life.
    Interpretation and limitations
    Record BSA and global scores; specialists commonly add PASI and DLQI. Correct for erythema underestimation in darker skin and document function independently.
  2. 02
    Phototherapy suitability assessment
    Why
    Identify photosensitising medicines, photodermatoses, skin-cancer risk, prior ultraviolet dose, eye risk and practical attendance barriers.
    Interpretation and limitations
    A high cumulative PUVA history or especially high skin-cancer risk may favour another treatment; newly started photosensitising medicine requires unit review before exposure.
  3. 03
    Systemic baseline blood and clinical screen
    Why
    Measure full blood count, renal and liver function, blood pressure, weight and agent-specific infection or metabolic risks before treatment.
    Interpretation and limitations
    The required panel depends on the selected medicine; abnormal renal, hepatic, haematological or blood-pressure results can change drug or dose and need documented action.
  4. 04
    Pregnancy, contraception and conception assessment
    Why
    Prevent teratogenic exposure and select a compatible strategy for all people whose reproductive plans affect treatment.

Treatment approach

01First-line phototherapyNarrowband UVB courseFirst stepFirst linePlaque or guttate psoriasis not controlled by topical treatment alone and no urgent instability.+
  1. 1Confirm diagnosis, extent, skin cancer and photosensitivity history, medicines, previous ultraviolet exposure, ability to attend and informed consent.
  2. 2Offer supervised narrowband UVB two or three times weekly; explain that three sessions weekly may achieve response faster while total course and doses remain unit-prescribed.
  3. 3At each visit report burns, new medicines and illness; use assigned shielding and do not add deliberate sun or home ultraviolet exposure.
  4. 4Third lineDo not continue routine maintenance. Choose another second- or third-line option after intolerance, inadequate response, rapid relapse, access failure or especially high skin-cancer risk.

Regimens, contraindications and interactions

NICE first-choice conventional systemic treatment for most people meeting systemic psoriasis criteria, using the lowest effective maintenance dose.

Methotrexate

Start incrementally, for example 5 to 10 mg orally once weekly, and increase to the effective dose up to 25 mg once weekly; assess after 3 months at target dose.

Never daily: name the weekly day and counsel about fatal overdose. Avoid pregnancy and major liver, marrow, renal or active-infection risk; reconcile trimethoprim and other interactions and monitor bloods.

NICE first-choice conventional systemic when rapid or short-term control is needed, for palmoplantar pustulosis, or specified conception circumstances.

Ciclosporin

Give 2.5 to 3 mg/kg/day orally in 2 divided doses; increase towards 5 mg/kg/day after 4 weeks for non-response, or sooner only when rapid control is necessary.

Monitor blood pressure, renal function, potassium, magnesium, lipids, infection and extensive interactions; do not use continuous treatment beyond one year unless exceptional specialist criteria apply.

NICE option when methotrexate and ciclosporin are inappropriate or have failed, and for pustular psoriasis under specialist care.

Acitretin

Use incremental oral dosing to a NICE target of 25 mg once daily; increase to at most 50 mg daily only when no other treatment options remain and assess response at 4 months.

Complications, monitoring and follow-up

  • Phototherapy units record dose, erythema, burns, shielding, missed sessions, new photosensitising medicines and cumulative exposure at every visit; suspicious lesions trigger assessment, not further ultraviolet dosing.
  • For conventional systemic treatment, follow agent-specific blood count, renal, liver, blood-pressure, pregnancy and infection protocols with one named team responsible for actioning every result.
  • Reassess systemic response at the NICE-specified target-dose point using baseline disease severity, high-impact function, DLQI or equivalent impact, arthritis control, adverse effects and the person's view.
  • Review vaccination and infection risk before and during immunomodulation, and give a clear contact route for fever, shingles, breathlessness, mouth ulcers, bruising or other agent-specific warning symptoms.
  • Maintain cardiovascular, smoking, alcohol, weight and mood assessment as appropriate, and avoid treating these as prerequisites for access to effective psoriasis care.

Special situations

Phototherapy is measured medicine

Dose depends on calibrated equipment, skin response and prior exposure. Commercial sunbeds and self-directed sunlight do not reproduce the unit's spectrum, governance or monitoring.

Attendance changes feasibility

Two or three weekday visits for weeks can be impossible because of work, caring, mobility or distance. NICE recognises access difficulty as a reason to offer another strategy.

Once weekly means one day

Methotrexate prescriptions, dispensing labels and patient cards should name the day in full. The repeated phrase never daily prevents a known fatal medication error.

Phenotype changes choice

Methotrexate suits many chronic plaques, ciclosporin offers faster control, and acitretin has a pustular role. Comorbidity and pregnancy potential can outweigh phenotype preference.

Scores need context

PASI can underweight difficult sites and under-recognise erythema in darker skin. Pair it with function, patient global assessment and quality-of-life change.

Common pitfalls

  1. 01

    Describing narrowband UVB as ordinary sunlight or recommending an unregulated tanning bed.

  2. 02

    Offering phototherapy without checking photosensitising medicines, previous skin cancer, cumulative exposure and ability to attend.

  3. 03

    Writing methotrexate without one named weekly day or failing to say never daily.

  4. 04

    Selecting a systemic drug from skin severity alone while ignoring arthritis, infection, organ function and conception plans.

  5. 05

    Using acitretin without the full three-year post-treatment pregnancy-prevention requirement where applicable.

  6. 06

    Continuing ineffective or toxic systemic therapy because a single score improved while function or safety worsened.

Practice

Two practice questions

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Question 1 of 2
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DermatologyOriginal SBA

Phototherapy first offer

An adult has widespread guttate psoriasis not controlled by appropriate topical treatment and can attend a supervised unit. Which NICE-supported option is most appropriate?

Choose one answer, then submit
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Sources and review status8 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.

  • NICE CG153: phototherapy and systemic psoriasis treatment
  • British Association of Dermatologists: narrowband UVB phototherapy
  • British Association of Dermatologists: oral PUVA phototherapy
  • MHRA: prevention of once-weekly methotrexate dosing errors
  • Methotrexate tablets Summary of Product Characteristics
  • Neoral capsules Summary of Product Characteristics
  • Acitretin capsules Summary of Product Characteristics
  • MHRA: oral retinoid pregnancy-prevention materials

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

Acitretin is considered when methotrexate and ciclosporin are unsuitable or failed, and for pustular forms; the MHRA pregnancy-prevention programme continues for three years after stopping where pregnancy is possible.
  • Targeted immunomodulatory treatments are consultant-initiated and supervised; screen infection, vaccination and reproductive risks and follow the current NICE technology appraisal for the selected agent.
  • Mouth ulcers, sore throat, unexplained bruising, bleeding, breathlessness or fever during methotrexate may indicate marrow, pulmonary or infectious toxicity and needs urgent review.
  • Rising blood pressure, reduced renal function, severe headache or interacting medicine exposure during ciclosporin requires prompt specialist assessment.
  • Pregnancy or possible conception during acitretin exposure, or within the mandated post-treatment prevention interval, requires immediate specialist teratology and pregnancy-prevention pathway advice.
  • A severe phototherapy burn, blistering, eye pain after PUVA or a suspicious changing lesion needs treatment interruption and urgent unit review.
    • Interpretation and limitations
    Acitretin has a three-year post-treatment pregnancy-prevention period where pregnancy is possible; methotrexate is contraindicated in pregnancy, while choices around conception need specialist advice.
  • 05
    Infection and vaccination screen before immunomodulation
    Why
    Identify active infection and complete agent-specific tuberculosis, hepatitis, HIV or vaccine assessment before immune suppression.
    Interpretation and limitations
    Testing follows the selected agent and protocol. Treat active infection and plan live vaccines before immunosuppression when possible; a negative screen does not remove later infection vigilance.
  • 06
    Serial response and toxicity measures
    Why
    Decide whether benefit justifies continuing exposure at the guideline-defined review point.
    Interpretation and limitations
    Compare PASI or global response, DLQI, high-impact function and arthritis with baseline while trending agent-specific labs; isolated score improvement cannot offset serious toxicity.
    • 02Alternative phototherapyLocal or oral PUVA decisionAlternativeSelected plaque disease or local palmoplantar pustulosis after specialist risk-benefit assessment.+
    1. 1Discuss alternatives and the cumulative squamous-cell carcinoma risk; risk rises with treatment number and later ciclosporin can add particular concern after high PUVA exposure.
    2. 2For oral psoralen, follow unit timing and dose, wear specified 100% ultraviolet-protective eyewear for at least 12 hours, and protect skin from additional UVA through windows and outdoors.
    3. 3Record every exposure and adverse event; do not improvise psoralen dosing or substitute commercial tanning equipment.
    03First-choice systemicMethotrexate for most eligible diseaseConventional systemic criteria met without a reason to prefer ciclosporin or avoid methotrexate.+
    1. 1Confirm baseline blood count, renal and liver status, infection, alcohol and liver risk, pregnancy status, interactions, vaccination and ability to follow once-weekly dosing.
    2. 2NICE uses incremental oral dosing, for example 5 to 10 mg once weekly, increasing to an effective dose up to 25 mg weekly; name one intake day and explicitly state never daily.
    3. 3Monitor according to the agreed specialist protocol, teach urgent toxicity symptoms and assess response after three months at the target dose; stop if NICE response criteria are not met.
    4. 4Use the lowest effective maintenance dose and coordinate rheumatology when active psoriatic arthritis changes the best systemic choice.
    04Alternative systemicCiclosporin, acitretin or targeted therapyAlternativeRapid control, palmoplantar pustulosis, conception context, contraindication, failure or phenotype-specific need.+
    1. 1Use ciclosporin first-choice when NICE rapid-control, palmoplantar-pustulosis or conception circumstances apply, monitoring renal function, blood pressure and interactions closely.
    2. 2Consider acitretin after methotrexate and ciclosporin are unsuitable or failed, or for pustular psoriasis, with incremental dosing and the full MHRA pregnancy-prevention programme.
    3. 3Consultant dermatologists initiate and supervise targeted immunomodulatory treatment under current NICE technology-appraisal eligibility, infection screening and agent-specific response rules.
    4. 4Offer continued adjunctive topical treatment and long-term safety registry participation where applicable; never combine systemic agents without specialist ownership.

    Highly teratogenic with MHRA pregnancy prevention and testing for 3 years after stopping where pregnancy is possible; monitor liver and lipids, avoid tetracyclines and excess vitamin A, and counsel on dryness.

    Content changes
    Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom