Narrowband ultraviolet B phototherapy

Several skin conditions (eg psoriasis, dermatitis, cutaneous lymphoma) respond favourably to measured doses of a specific band of sunlight—narrowband ultraviolet B (UVB) phototherapy (wavelength 311 nm).

Phototherapy primarily works by inhibiting the immune and inflammatory pathways in the skin.

Patients generally receive phototherapy two to three times a week for a few months—this is a significant time commitment that may affect adherence. Therapy is limited to patients who are physically able to enter the treatment unit and stand in it for 5 to 10 minutes. Phototherapy is usually reserved for adults and older children. However, children as young as 6 years can be treated with the support of an experienced phototherapy nurse.

Phototherapy is often used in combination with topical therapy. Patients should not apply agents that block UV light (eg calcipotriol, sunscreen) immediately before treatment. Combination treatment with acitretin increases the efficacy of narrowband UVB when treating psoriasis.

Adverse effects of phototherapy include dose-related erythema (blisters can occur if severe) and hyperpigmentation. Evidence of the standard doses of phototherapy increasing the risk of skin cancer is lacking.