Phototherapy (light therapy) has been known and used since ancient times. Exposing the skin to light slows the growth of affected skin cells and improves the condition of the skin in psoriasis.

In the majority of patients, sun radiation proves favourable and visibly reduces the skin manifestations. Interestingly, phototherapy can also be used in patients in whom exposure to sun light may make the symptoms worse. This is because light lamps emit a safe and beneficial range of ultraviolet light.

Phototherapy needs to be applied consistently and regularly, under permanent medical control. Like any other medical therapy, phototherapy is associated with a risk of side effects, including phototoxicity, accelerated skin ageing, acute inflammation of cornea and conjunctiva, and skin cancer.

Phototherapy in psoriasis is delivered through various methods based on UVA and UVB light.


PUVA (psolaren + PUVA)

This is the only treatment method for psoriasis that combines a light-sensitizing medication psoralen (administered orally) and ultraviolet light A (UVA). Patients with psoriasis take a dose of psoralen and then attend a session of phototherapy with an UVA lamp at a healthcare centre. The patient is given protective glasses to wear during the session. Also, patients have their eyes and liver function tested after a series of light therapy sessions (3-4 sessions a week). As a precaution, the skin cannot be exposed to sunlight directly after attending a light therapy session. PUVA is typically used in patients with 10%-15% of the total skin area affected by psoriasis. Long-term phototherapy is associated with increased risk of itching, headaches, nausea, and skin cancer.

UVB phototherapy

UVB phototherapy (either broadband or narrowband ultraviolet light) in psoriasis is  safer than PUVA and can be recommended for patients with psoriasis and concomitant liver or eye problems. Patients typically experience an improvement of symptoms after a few UVB therapy sessions. Just like PUVA, UVB phototherapy should be delivered under medical supervision. Exposure to UVB light may cause spontaneously resolving skin redness (erythema) and itching. Narrow-band UVB therapy in the 311 – 312 nm spectra is considered most effective for managing psoriasis.
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