Background
Although many patients with psoriasis may be capable of adequately controlling their disease with the use of topical treatments alone, often these interventions are insufficient and disease severity dictates the need for alternative options. While systemic and biologic treatments are heavily relied on for severe and widespread skin disease, these medications do come with risks of systemic side effects and immunosuppression that many patients may not be willing or able to assume. Phototherapy serves as a reasonable and effective treatment option for patients requiring more than topical medications and/or those wishing to avoid systemic medications or simply seeking an adjunct to a failing regimen.

Scope
This section covers the use of phototherapy in the treatment of psoriasis in adults; psoriasis treatment in the pediatric population is addressed in the Joint American Academy of Dermatology–National Psoriasis Foundation Guidelines of Care for the Management and Treatment of Psoriasis in Pediatric Population (in preparation).

Targeted UV-B
Targeted UV-B treatments such as excimer laser (308 nm), excimer light (308 nm), and targeted NB-UV-B light (311-313 nm) are well suited and recommended for treating localized psoriatic lesions. An advantage of targeted phototherapy is that it spares unaffected skin, permitting higher doses, faster clearing, and less risk.

LINK: https://www.jaad.org/article/S0190-9622(19)30637-1/fulltext