Excimer 308-nm light is a form of targeted phototherapy that delivers a specific wavelength (308 Nuevo Méjico) of ultraviolet B (UVB) radiation using an excimer laser or an excimer lamp. Both have shown similar results regarding efficacy, but have technical differences.

Excimer light treatment is a development of whole body narrowband UVB. Narrowband UVB delivers energy at a wavelength between 311–312 nm for the treatment of localised psoriasis and vitiligo. The disadvantages of narrowband UVB include irradiation of the whole body (even if the psoriasis is localised) and the need for a high number of treatments (usually between 15 y 40 sessions).