09/18/2026
308 nm vs 311 nm — what’s the difference?
308 nm excimer is designed for targeted treatment. Instead of exposing a large area of skin, UVB is delivered directly to specific lesions.
Because the surrounding skin can be avoided, a higher dose can be delivered to the selected treatment area. For small, localized patches, this can mean shorter treatment sessions and, in some cases, a faster response.
In one clinical study of localized vitiligo, 308 nm excimer treatment reached 25% repigmentation after an average of about 19 sessions, compared with about 26 sessions with targeted 311 nm NB-UVB.
311 nm narrowband UVB is usually more practical when larger or multiple areas need treatment. Panels and full-body systems can cover much more skin during a single session, which would be inefficient to treat spot by spot with an excimer device.
The difference is less about the number and more about the treatment area. 308 nm is used for precise, localized treatment, while 311 nm is commonly used when broader skin coverage is needed.
Neither wavelength is automatically “better.” Results depend on the condition, treatment area, device, dose, and treatment protocol.