Phlebodium decumanum, often referred to as "calaguala," is a tropical fern whose extracts have been traditionally used in South American and Central American herbal medicine. While traditional use does exist, there is also a growing body of scientific literature supporting its benefits for general skin care, particularly due to its antioxidant and photoprotective properties.

Scientific studies, primarily conducted in vitro and in animal models, indicate that Phlebodium decumanum contains several bioactive polyphenols and flavonoids that possess antioxidant activity. These compounds can help protect skin cells from oxidative stress, which is a contributing factor to skin aging and damage caused by ultraviolet (UV) radiation. Some small clinical studies and reviews have examined extracts of the related fern Polypodium leucotomos (which has similar constituents) for their ability to reduce UV-induced erythema, support skin barrier function, and decrease the risk of photodamage; however, direct clinical evidence for Phlebodium decumanum itself is more limited.

Overall, the use of Phlebodium decumanum in skin care is supported by biological plausibility and preliminary evidence, but higher-quality clinical trials are still needed. The current evidence base merits a moderate score of 3 out of 5.