Polypodium leucotomos is a tropical fern whose extract has been studied for its photoprotective and anti-inflammatory properties, particularly in dermatology. Several small clinical studies and reviews suggest that oral supplementation with Polypodium leucotomos extract may benefit patients with psoriasis, especially in the context of phototherapy. The rationale is that the extract contains polyphenols with antioxidant and immunomodulatory effects that may reduce the inflammatory response and oxidative stress associated with psoriasis pathogenesis.

Some clinical trials have investigated the use of Polypodium leucotomos as an adjunct to UVB phototherapy, finding that it may reduce UV-induced skin damage and extend the duration of remission in psoriasis patients. However, most studies are limited by small sample sizes and lack of large, well-controlled trials. The evidence for its effectiveness as a standalone treatment for psoriasis is weak, and most dermatological guidelines do not formally recommend its use outside of adjunctive therapy during phototherapy.

In summary, there is some scientific support for the use of Polypodium leucotomos in psoriasis, particularly as an adjunct to phototherapy, but the overall quality and quantity of evidence is limited (rated 2/5). Further rigorous studies are needed to confirm efficacy and optimal usage.