Animals can use medicinal plants to heal themselves

"...A wild male Sumatran orangutan named Rakus was observed applying sap and chewed leaves from a medicinal plant to his facial wound. This is believed to be the first documented case of a wild animal actively using a medicinal plant to treat an injury."

The paper published last year in Nature:

Active self-treatment of a facial wound with a biologically active plant by a male Sumatran orangutan