When creams alone don't keep psoriasis in check, a dermatologist may suggest phototherapy — controlled doses of ultraviolet light that calm plaques from the inside out. It's an established, effective option, but it's a medical treatment, not a tanning session. Here's how UVB phototherapy works, when it's used, and what to know about safety.
UVB phototherapy treats psoriasis with controlled ultraviolet B light in a clinic. Narrowband UVB (311 nm) is a first-line option; a 308 nm excimer laser targets individual stubborn plaques. It's used for widespread or topical-resistant psoriasis, given 2–3 times a week under supervision. It is not a tanning bed: the dose and wavelength are controlled, your eyes are protected, and exposure is tracked. The clearest skin-cancer risk is with PUVA, not UVB.
UVB phototherapy uses controlled ultraviolet B light to calm psoriasis — as a supervised medical treatment, not tanning. The light dampens the overactive immune response and slows the excessive skin-cell turnover behind plaques. Narrowband UVB (311 nm) is the go-to; a 308 nm excimer laser targets localized plaques (palms, soles, scalp, stubborn spots). It's typically used when topicals aren't enough or psoriasis is widespread, given 2–3 times weekly for a few minutes per session over several weeks, with the dose tracked and eyes protected. It is not the same as a tanning bed — those aren't a substitute and carry their own risks. Skin-cancer risk is mainly linked to PUVA (a UVA-based therapy), not narrowband UVB. Always done under a dermatologist's care.
What UVB Phototherapy Is
Phototherapy (light therapy) treats psoriasis by delivering specific, measured doses of ultraviolet light to the skin in a medical setting — harnessing the therapeutic part of what sunlight does, without the guesswork. Several forms exist. Broadband UVB (290–320 nm) is the older approach; narrowband UVB (NB-UVB, 311 nm) has largely replaced it as a more effective, first-line choice. The 308 nm excimer laser is a targeted UVB source that treats individual plaques while sparing the skin around them. There's also PUVA, which pairs a light-sensitising drug (psoralen) with UVA — effective, but used less often now because of a higher long-term risk profile.
However it's delivered, the mechanism is similar: UVB light calms the overactive immune signalling in psoriasis (dialling down the inflammatory pathways that drive it) and slows the runaway skin-cell turnover that builds up plaques and scale.
When Is It Used?
For many people, topical treatments are enough to keep psoriasis comfortable. When they're not — if itching and scaling persist, or psoriasis is widespread — a dermatologist may add phototherapy. It's often considered for moderate-to-severe disease (for instance, when more than about 10% of the body surface is affected), and it's a common choice for stable plaque psoriasis.
The targeted excimer laser is especially useful for localized or hard-to-treat areas — the palms and soles (palmoplantar psoriasis), the scalp, or a few persistent plaques — because it concentrates the dose where it's needed. Whether phototherapy is right, and which type, is a decision your dermatologist makes with you.
How A Course Works
Phototherapy is usually given in a dermatology clinic, about 2 to 3 times a week. Each session is short — often just seconds to a few minutes — and the dose is increased gradually as your skin adapts, over a course that runs several weeks.
Safety is built into the routine: your cumulative UV dose is tracked and capped (sessions aren't simply extended or piled on), your eyes are protected with goggles, and sensitive areas can be shielded. Between sessions, you're advised to protect your skin from extra UV so you're not adding uncontrolled exposure on top of the treatment.
Is It Safe?
It is not a tanning bed. Medical phototherapy uses controlled wavelengths and doses under supervision; a tanning salon does none of that and is not a substitute — never try to self-treat psoriasis with tanning beds or deliberate sunbathing, which carry their own skin-cancer and ageing risks.
The main considerations with UVB are short-term redness or burning if the dose is too high, and, over the long term, some photoageing — which is exactly why the dose is measured and your eyes are protected.
On skin cancer: the clearest risk is linked to PUVA (the UVA-plus-psoralen therapy), not narrowband UVB. For NB-UVB, large studies haven't clearly shown an increased skin-cancer risk — a key reason it's preferred — though UV is always treated with respect, so exposure is monitored and limited.
Who it's for: mainly adults, but NB-UVB can be used in children in selected cases (for example, when topicals haven't worked) under specialist care, and it's often considered relatively suitable in pregnancy — decisions your doctor makes individually. A dermatologist also screens suitability, since some conditions and medications make phototherapy inappropriate.
A Note On Deeper Skin Tones
Phototherapy works across the skin-tone spectrum — including medium-to-deep skin — but the starting dose and increments are tailored to your skin type, since more melanin changes how skin responds to UV. A good clinician calibrates the protocol accordingly. It's also worth remembering that psoriasis on deeper skin can settle into lasting light or dark marks, so managing inflammation well matters for both comfort and even tone.
What This Means For You
Phototherapy is a well-established, effective tool in the psoriasis toolkit — but it's a supervised medical treatment, not something to improvise at home or approximate with a tanning bed. If topicals aren't keeping your psoriasis under control, it's worth asking your dermatologist whether phototherapy suits you, and how it fits alongside other options. Understanding what drives psoriasis — and how severity is assessed — helps you have that conversation, including about trickier spots like the nails.
- Narrowband UVB (311 nm) — the first-line phototherapy for psoriasis.
- Excimer laser (308 nm) — targets localized, stubborn plaques.
- 2–3 sessions/week — short, dose-controlled, over several weeks.
- Not a tanning bed — supervised, measured, eyes protected.
- Skin-cancer risk is mainly PUVA's — not clearly shown for NB-UVB.
UVB phototherapy is a supervised, effective psoriasis treatment — not a tanning session. Narrowband UVB (311 nm) is first-line and the 308 nm excimer laser targets stubborn plaques; both calm the overactive immune response and slow plaque build-up. It's used when topicals aren't enough or psoriasis is widespread, given 2–3 times weekly with the dose tracked and eyes protected. Skin-cancer risk is chiefly linked to PUVA, not NB-UVB — but UV is always handled carefully, which is why it's done under a dermatologist's supervision, never with a tanning bed.
Phototherapy is a great example of "same idea as the sun, done safely" — controlled wavelengths, measured doses, protected eyes, tracked exposure. That's also why the tanning-bed shortcut is a genuinely bad idea: it borrows the appeal without any of the safeguards. Our steer is simple — if creams aren't cutting it, ask your dermatologist about phototherapy rather than chasing UV on your own, and if you have deeper skin, make sure the dosing is tailored to you.
Frequently Asked Questions
What is UVB phototherapy for psoriasis?
UVB phototherapy is a medical treatment that delivers controlled doses of ultraviolet B light to psoriasis-affected skin in a clinical setting. The most common form, narrowband UVB (311 nm), is a first-line phototherapy; a 308 nm excimer laser can target individual stubborn plaques. The light calms the overactive immune response and slows the excessive skin-cell turnover that drives psoriasis plaques.
Is phototherapy the same as using a tanning bed?
No — and this is important. Medical phototherapy uses specific, dose-controlled wavelengths under a doctor's supervision, with your cumulative exposure tracked and your eyes protected. A tanning bed is not a substitute: it isn't dosed for psoriasis, isn't supervised, and carries its own skin-cancer and ageing risks. Never try to self-treat psoriasis with tanning beds or deliberate sunbathing.
Does UVB phototherapy cause skin cancer?
The clearest skin-cancer risk is with PUVA (a psoralen-plus-UVA therapy), not UVB. For narrowband UVB, large studies have not clearly shown an increased skin-cancer risk, which is one reason it's preferred. That said, any UV exposure is treated with respect: your dermatologist tracks and limits your cumulative dose, protects your eyes, and photoageing remains a consideration — so it's always done under medical supervision.
How often are phototherapy sessions?
A typical course involves sessions about 2 to 3 times a week, each lasting only seconds to a few minutes, in a dermatology clinic. The dose is increased gradually and your skin is monitored, with a course running over several weeks. Between sessions, you protect your skin from extra UV. Your dermatologist sets and adjusts the schedule.
Can children have phototherapy for psoriasis?
It's used mainly in adults, but narrowband UVB can be used in children in selected cases — for example, when topical treatments haven't worked — under specialist supervision. A dermatologist assesses whether it's suitable for each person, since some conditions and medications make phototherapy inappropriate. Decisions for children are always made with specialist care.
Boldpurity Science Team
Boldpurity is a clinical skincare brand with in-house cGMP manufacturing in Hyderabad, India, formulating evidence-led skincare for medium-to-deep skin tones. Content is prepared and science-reviewed by the Boldpurity Science Team.
Editorial Process
Articles are drafted from peer-reviewed dermatology literature and clinical guidelines, science-reviewed for accuracy, and kept at an education level. We frame phototherapy as a supervised medical treatment, distinguish it clearly from tanning, report risks honestly, and make no product claims.
Reference Policy
Claims are supported by cited sources (see References), including dermatology guidelines on phototherapy for psoriasis and reviews of its safety profile.
Medical Disclaimer
This article is general information, not medical advice, and does not diagnose or treat any condition. Phototherapy is a medical treatment that must be prescribed and supervised by a dermatologist; it is not equivalent to, and should never be replaced by, tanning beds or deliberate sun exposure. Discuss suitability, benefits and risks with your doctor.
This article is educational, does not diagnose or treat any condition, and does not recommend specific products. Phototherapy is a medical treatment prescribed and supervised by a dermatologist and is not equivalent to tanning beds or deliberate sun exposure, which are not safe substitutes. Consult a dermatologist about whether phototherapy is appropriate for you and about its benefits and risks.
- Elmets CA, et al. Joint AAD–NPF guidelines of care for the management of psoriasis with phototherapy. J Am Acad Dermatol. 2019.
- DermNet. Phototherapy. dermnetnz.org.
- Zhang P, et al. A clinical review of phototherapy for psoriasis. Lasers Med Sci. 2018.
- American Academy of Dermatology (AAD). Psoriasis: phototherapy. aad.org.
