Since ancient times, people have been fascinated with mercury, due to the metal's glistening silver color and its liquid state at room temperature. The ancient Chinese thought that red mercury sulfide, a compound of mercury, had the ability to increase longevity and vigor, and medieval Arabs used it in ointments to treat skin diseases [sources: Norn, et al., Andrews].
Mercury became a go-to treatment when syphilis began to spread through Europe in the late 1400s. The disease's symptoms — genital sores, followed by foul abscesses, ulcers that could eat into bones and destroy facial features, severe pain and eventually death — quickly made it one of the most feared diseases around [source: Frith]. Doctors applied mercury to patients' skin; injected it into their bodies or had them swallow it or bathe in its fumes.
Mercury actually did have some effectiveness as a treatment, since it kills the spirochete bacteria that causes the disease [source: Stromberg] However, it may have done more harm than good to the patients, because the metal is a powerful toxin that damages the kidneys, causes brain damage and may lead to death [source: Columbus].