Polypodium Leucotomos is a herb commonly referred to as either 'Fernblock' or 'Heliocare' and is marketed as being a skin health supplement for sensitive skin. Most of the studies on Polypodium Leucotomos do note that it appears to have a variety of protective effects against UV(B) induced skin cell radiation, which confers protective effects agains the sun despite absorbing the radiation (something like sunscreen would prevent radiation from being absorbed, and confer protection by omitting the radiation)

The benefits, mechanistically, are part anti-oxidant and part anti-inflammatory but may be highly related to an induction of p53; a protein that is sometimes known as anti-tumor, but also appears to suppress inflammation while protecting the genome (DNA) from damage.

What makes Polypodium novel is that is works after oral ingestion, and that DNA protection has been found in rats following oral ingestion.

Human interventions note that it seems to beneficially influence most skin conditions, with fairly reliable suppression of erythema (reddening of the skin in response to UV radiation) and can help with persons who are hypersensitive to sunlight and suffer from "polymorphic light eruptions", a delayed onset itchiness and reddening (not necessarily a sunburn).

It has been investigated for its abilities to help vitiligo (with not-too-potent results) and for upper respiratory tract infections, with at least one study suggesting promise.

It definitely shows promise and is novel, but is not a highly supported herb when looking at interventions.