Interesting and gross. The History of Thieves Oil
Europeans began producing essential oils in the 12th century. During the Plague of the 15th century, certain thieves robbed the dead without becoming infected. Finally, four thieves were captured in Marseilles, France, and charged with robbing the dead and dying victims of the plague.
At the trial, the magistrate offered them leniency if they would reveal how they managed to avoid contracting the dreaded infection, in spite of their close contact with infected corpses. It was disclosed that these thieves were perfumers and spice traders who had rubbed themselves with a concoction of herbs making them immune to their deceased and moldy victims.