What advantages does narrowband UVB have over PUVA?

Narrowband UVB does not have the risks, side effects, and inconvenience of taking oral psoralens, including nausea, vomiting, dizziness, headache, insomnia, depression and anxiety, hepatotoxicity, drug interactions, allergic reactions, photoallergic reactions, PUVA keratoses, PUVA lentigines, PUVA pain, transient nail pigmentation, photoonycholysis, facial hypertrichosis, licheoid eruptions, photosensitivity for 24 hours (even through windows), risk of cataracts, increased risk of melanoma and other skin cancers including genital skin cancers, narrow window of treatment after taking medication (1 to 2 hours), variability of tissue response depending on medication absorption and distribution (which is time sensitive), and need to wear sunglasses and avoid natural sunlight after taking medication for 24 hours. Narrowband UVB has not demonstrated increased carcinogenicity, thus far in humans, and the efficacy is similar. However, increased carcinogenicity has been noted in rats, and long-term follow-up is not yet available.

Laube S, George SA: Adverse effects with PUVA and UVB phototherapy, J Dermatol Treat 12:101–105, 2001.