Here's another anti-infection remedy that involves tree bark. Back in the 1500s, when syphilis was raging through Europe, desperate sufferers — or at least, the ones who hadn't yet been poisoned with mercury — tried an extract called guaiacum, or holy wood. It came from a tree native to the Caribbean and the Americas. Part of the treatment's appeal was that it came from the New World, where Europeans assumed that their explorers had contracted the disease and brought it back across the ocean [source: Edward Worth Library].
The theory at the time was guaiacum would unclog the body's excretory system and pores, allowing the infected blood to be purified [source: Varey and Chabran]. Syphilis patients were given the bark extract in a hot drink, and then subjected to a "sweating cure" [source: Edward Worth Library].
Guaiacum became so popular that a conspiracy theory developed that doctors weren't prescribing it because it might cure patients and cut physicians' income. It became even more expensive because the Holy Roman Emperor Charles V. awarded an importation monopoly to the banking house of Fugger. But by the 1540s, the demand was falling off, because people began suspecting that it didn't work. They continued using mercury until 1910, when arsenic came into vogue as the cure for syphilis [sources: Varey and Chabran, Frith].