A hydrophilic extract of Polypodium leucotomos has been used in Central and South America''s traditional folk medicine to ameliorate different skin and joint diseases. An extract of Polypodium leucotomos has been commercialized in Spain under the brand name Difur® and used for the treatment of skin diseases such as psoriasis and vitiligo. In this study, a pharmacological study has been carried out in order to show the immunological basis of the curative properties attributed to this extract.