The best candidate Dr. Dalton found for a universally distasteful smell was something called “U.S. Government Standard Bathroom Malodor,” a substance that was designed to mimic the scent of military field latrines, in order to test cleaning products. She chose the aromatic liquid as the base of her stink-bomb recipe. The resulting formula, which she called “Stench Soup,” may well be the worst smell ever created.

Mary Roach, a science writer, is one of the few humans who’s tried inhaling Stench Soup. In her 2016 book “Grunt: The Curious Science of Humans at War,” she described the aroma as “Satan on a throne of rotting onions.”

Is Stench Soup really the worst smell in the world? That’s hard to say, in part because researching bad smells can be difficult. Chemists tell cautionary tales about a substance called thioacetone, which in 1889 was the subject of experiments in a lab in Frieberg, Germany. One thioacetone reaction produced a smell so bad that it spilled out of the lab and swept through the city, causing widespread panic and evacuation, along with a lot of people being sick in the streets.