Four Thieves Vinegar is a legendary remedy that has been sold in France since the early 18th century. According to the legend, four thieves who were "recruited" to bury plague victims in Marseilles made a concoction of crushed garlic and wine vinegar which they drank to fortify themselves as they worked (one imagines also that the smell of their drink may have numbed them against the odor of decomposing bodies as well). Their resistance to the plague became a subject of amazement, and the recipe for the vinegar was thus uncovered.

Vinegar is a reasonably effective antibacterial agent, as is garlic. Garlic taken in good quantities is also an immune system enhancer, which could account for the decreased susceptibility of the thieves to the virus.

One commonly finds reference these days to various recipes for Four Thieves vinegar which involve numerous combinations of herbs known to have antibacterial and antiseptic properties. Some refer to a version of the tale in which the four thieves had in their number the son of an herbalist, who gave him a recipe which included many herbs. However, most proponents of the more complex recipes and the herbalist's son story are selling a proprietary mixture of some sort - although the demographic range of such sellers is interesting enough, as it includes voudoun gewgaw merchants, New Age herbalists, neopagan and Wiccan supply shops, and redneck survivalist/paranoiacs. All but the last recommend it as a kind of black magic repellant. The survivalists swear by its ability to knock out airborne weaponized plagues when burned aromatherapy-style. Nevertheless, your great-great-great-great-grandma's Four Thieves vinegar was likely simply a head of garlic, crushed and cold-macerated with a litre of strong red wine vinegar.