Phototherapy is a treatment of affected skin with ultraviolet (UV) rays. It has an anti-inflammatory effect and inhibits the accelerated rate of skin cell reproduction and maturing.


Narrow-band UVB therapy with rays having the wavelength of 311nm are most used to treat psoriasis. When psoriasis is more severe, UVA radiation in combination with a photosensitizer (psoralen), which is called photochemotherapy or PUVA (Psoralen + PUVA), is used. The photosensitizer can be taken by the patient in the form of tablets or capsules or applied to the skin with an ointment or in a bath. It usually requires the patient to undergo between 20 and 30 irradiations to achieve remission, which are performed in special therapy centers.

UV radiation is carcinogenic and increases the risk of developing skin cancer. The number of radiation treatments is limited to 300 photochemotherapies overall.

Patients with psoriasis are advised against sun or solarium exposure as they have carcinogenic properties.

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