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Author: Dr Amanda Oakley, Dermatologist, Waikato Hospital, Hamilton, New Zealand, 2001. Updated October 2015.
Narrowband UVB is the most common form of phototherapy used to treat skin diseases. "Narrowband" refers to a specific wavelength of ultraviolet (UV) radiation, 311 to 312 nm. UVB phototherapy was formerly provided as a broadband source (290 to 320 nm).
The narrowband range of UV radiation has proved to be the most beneficial component of natural sunlight for psoriasis. Narrowband UVB may also be used in the treatment of many other skin conditions including atopic eczema, vitiligo, pruritus, lichen planus, polymorphous light eruption, early cutaneous T-cell lymphoma and dermographism.
Compared with broadband UVB:
Narrow-band UVB can result in burning, just like sunlight and broadband UVB. Frequent emollients should be applied to burned skin, and if recommended by the therapist, topical steroids. It sometimes provokes polymorphous light eruption.
Long term exposure to ultraviolet radiation ultimately causes skin ageing and skin cancers. In theory, less UV exposure occurs because the patient is only exposed to therapeutic wavelengths. Although the risk from narrow-band UVB is unknown, research to date suggests it is no more risky than broadband UVB and probably less risky than photochemotherapy (PUVA).
Patients attend for phototherapy two to five times weekly. If whole-body treatment is recommended, the patient is placed in a specially designed cabinet containing fluorescent light tubes.
The patient stands in the centre of the cabinet, undressed except for underwear, and wears protective goggles. Usually the whole body is exposed to the UVB for a short time (seconds to minutes).
Shorter bulbs can be used for localised UVB treatment, eg of hands and feet or a small body region.
The amount of UV is carefully monitored by the phototherapy staff. A number of protocols exist depending on the individual's skin type, age, skin condition and other factors.
The skin may remain pale or turn slightly pink (the Minimal Erythemal Dose) after each treatment. Let your therapist know if you experience any discomfort.
Patches of psoriasis generally start to become thinner after five to ten treatments. Most patients with psoriasis require 15 to 25 treatments to clear. Results vary.
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