Arallyn Primm writes at Mental Floss:
No one likes to be sick or suffering. Humans have tried to fight against disease and affliction since we could first comprehend “Hey, I ate that root, and now I don’t feel like death!” In the course of trying to find new cures for medical problems, or perceived medical problems, we’ve stumbled more than a few times along the way. Most of the time, treatments simply didn’t work, and were no more harmful than what they were meant to “cure.” Sometimes, though, the medicine was even worse than the condition itself.
1. To cure rabid human or dog bite
To his credit, Pliny the Elder discounted many purely-magical folk cures in his Natural Histories (not to mention writing entire chapters against the eating of infant brains), and was a proponent of several treatments which we now know to have some merit, such as aloe vera to dress burns.