The skin of frogs and toads is an ambulant pharmacopoeia with hundreds of structurally different biologically active substances identified in the past few decades. This arsenal has the double role of fending off bacteria and fungal pathogens that otherwise would thrive on the soft and humid skin and of defending the animal from larger predators. The "poison frogs" of the family Dendrobatidae—native to the rainforests of South and Central America—have evolved the ability to store in their skin the poisonous lipophilic alkaloids they ingest feeding on ants and other arthropods and to secrete them when challenged. It had been assumed that the sequestered poisons were simply shuttled to the skin, but in the September 1 PNAS, John W. Daly and colleagues at the National Institute of Diabetes and Digestive and Kidney Diseases show that these amphibians actively metabolize the alkaloids into more poisonous compounds (PNAS, DOI:10.1073/pnas.1834430100, September 1, 2003).