Polypodium leucotomos, a tropical fern extract, has been investigated for its photoprotective and anti-inflammatory properties in various skin conditions, including rosacea. Scientific evidence supporting its use in rosacea is limited but emerging. Several small clinical studies and reviews have noted its antioxidant and immunomodulatory effects, which may help reduce skin inflammation and protect against UV-induced exacerbations commonly seen in rosacea patients. For example, studies such as those by Middelkamp-Hup et al. (2007) and El-Haj & Goldstein (2020) have shown that oral supplementation with Polypodium leucotomos can reduce erythema and improve skin barrier function in UV-exposed skin. While these studies do not focus exclusively on rosacea, they suggest mechanisms—such as reduction of oxidative stress and inhibition of pro-inflammatory cytokines—that are relevant to the pathogenesis of rosacea.

However, there is a lack of large, well-controlled clinical trials directly evaluating Polypodium leucotomos specifically in rosacea patients. Most supporting evidence is extrapolated from its general effects on photodermatoses and inflammatory skin diseases. Therefore, while its use in rosacea is scientifically plausible and supported by some preliminary evidence, it cannot be considered a fully validated treatment, and the overall strength of evidence is modest.