Humans have been fighting lice infestations for millennia, and, until the advent of modern agents in the mid–20th century, pediculicides commonly contained mercury.
It has been reported that the use of mercury-based delousing therapies began as early as the Middle Ages. Confirmation of this use is provided by the mummified remains of a former King of Naples—Ferdinand II of Aragon—who died in 1496. His pubic and scalp hairs harbored high concentrations of mercury, as well as adherent nits and louse body fragments. Mercury was notably absent from the cranial and body cavities, and was detected only within the lice-infested regions, suggesting that the mercury was applied topically to provide relief from the infestation.1