Traditional remedies for common disorders have been known for centuries, but insight into their mechanism of action is often limited. In this issue of the JCI, Joost Schalkwijk's research group at the Radboud University Nijmegen Medical Centre in The Netherlands advances our understanding of why topical coal tar is an effective treatment for atopic dermatitis (AD), both rationalizing the use of this traditional medicine, and providing the scientific basis for new therapeutic approaches.