Allen Wittman and Andrew Masters are two grown men who make a living selling bathroom humor.

In 2005, the two former engineers founded Liquid Ass Novelties, LLC, in North Carolina. At the time, their entire business was based on selling a spray that comes in a one-ounce plastic bottle bearing the company’s name. It’s exactly what you’d expect: A water-based stench capable of emptying rooms in a matter of minutes.

“It’s like if you stuck your nose up to an asscrack of a plumber who hasn’t showered in three days,” Wittman says.

Wittman invented the spray in his teenage bedroom when he was in high school and tested it out by pouring four ounces into a heat radiator in a foyer bathroom near the gym, where a basketball game was ongoing in the dead of winter. By halftime, the doors to the school were open in an attempt to rid the room of the smell, despite the snowfall.

Decades later, Wittman met Masters in the electrical department in a trucking company based in Illinois. They became friends who shared a love of practical jokes, and one day decided to use Wittman’s remaining stash at an office ice cream social, effectively ruining it.

When the company eventually eliminated their positions, the two decided they could probably make a living out of their stinky product. They figured their target market would be similarly-minded pranksters eager to cause a little smelly mayhem. They were right, and had plenty of success with that audience, but to Wittman and Masters’ surprise, they also managed to reach customers with more noble pursuits.

Katherine Ellen Foley A tiny bottle packs a powerful punch.

Researchers, hospitals, and programs designed to train medical professionals routinely order Liquid Ass. The stench so realistically mimics the human colon, it’s the perfect training tool to teach medical responders how to maintain focus and professional demeanor in the midst of a truly overwhelming smell. And because the stench is universally offensive, psychologists have found it’s the perfect tool for studying the effects of disgust on all sorts of human behavior, from political decision-making to health care choices.

Practice smells

High-tech medical mannequins and simulation labs—rooms designed to imitate various medical emergencies—are increasingly popular as teaching tools in medical and nursing schools, but they’re usually incapable of replicating the full range of smells that can come from the human body.

That’s why Kata Conde, an assistant nursing professor at MidAmerica Nazarene University in Kansas, started buying Liquid Ass for the simulation lab she runs for her students. It’s the only product she’s found that accurately captures the smells that come from our bowels, and she would know: she had a 30-year career as a nurse before becoming an instructor. Conde now uses Liquid Ass in teaching scenarios in which a patient has soiled themselves while trying to get out of a hospital bed, complete with chocolate icing to set the scene. It’s also good for practicing bowel surgeries, like colostomies, where surgeons divert some of the large intestine to a new hole in the abdomen.

“The smell hits you like a huge wall,” she says. “It’s something people react to when they first experience it. We see all kinds of faces.” In a real-life scenario, any kind of reaction to a stench like wrinkling or covering your nose would make a patient understandably embarrassed and uncomfortable. To successfully complete the simulation, students have to demonstrate that they’re capable of giving adequate care while maintaining professionalism.

“The smell hits you like a huge wall. It’s something people react to when they first experience it. We see all kinds of faces.”

Conde first heard of Liquid Ass at a professional conference, where it was recommended it to her by a nursing instructor at another university. Wittman and Masters said they’ve also had orders from paramedics, Cedars-Sinai Medical Center in Los Angeles, and Pocket Nurse, a medical-supply company based in Pennsylvania.

Liquid Ass even made its way into military training operations, as Mary Roach describes in her book Grunt. It’s a key ingredient in fake bowels filled with dyed oatmeal, used in a device called a Cut Suit, a creation of a training company called Strategic Operations in San Diego, California which trains some members of the US military. The Cut Suit is a wearable prop that realistically mimics wounds; it starts off looking like healthy skin, and when you cut into it, it looks and smells like a real body would if it were cut open. The suits have been used, for example, by Navy medics practicing attending to wounded soldiers during an ongoing battle.

An influential emotion

Liquid Ass is also helping scientists learn about the nature of one of our oldest, instinctual emotions: disgust.

Disgust is a universal emotion ingrained into us by years of evolution. It’s an unpleasant feeling triggered by anything we should avoid for health reasons. Bodily fluids like blood, vomit, urine, or feces are fantastic ways of transmitting disease. Any cue that we’re near those substances sets off a natural aversion reaction, recognizable by a quickened heartbeat, sweaty palms, and a sickening feeling in the pit of the stomach.

Most people don’t feel deep disgust, or encounter these actually dangerous substances, on a regular basis. However, it’s likely that we do experience some degrees of disgust every day in ways we don’t notice, but still shape our behavior.

“A large proportion of human behavior is driven by avoidance,” says Nathan Consedine, a professor of psychology at the University of Auckland in New Zealand. Broadly, Consedine says, when people feel disgusted, even if it doesn’t register at a conscious level, they’ll avoid confronting the thing that is disgusting them.

Disgust is so deeply ingrained in us—likely because of its ancient utility—it’s still capable of influencing our behavior.

“Before we had developed any theory of disease, disgust prevented us from contagion,” David Pizarro a philosopher and psychologist based at Cornell University, told New Scientist. Now that we understand how disease actually spreads, there’s less of a need for this emotion. And yet, it’s so deeply ingrained in us—likely because of its ancient utility—it’s still capable of influencing our behavior. Consedine and his team, for example, had participants answer questionnaires regarding their feelings about bowel diseases and sexually transmitted infections, and then again in rooms that have been sprayed with Liquid Ass. The stench puts participants in a “disgusted” state, which, the researchers found, can cause some people with these conditions to delay seeking treatment.

Pizarro and others have found that disgust induced by a foul smell can affect how judgmental people are of minority groups, how conservative they are, or whether or not they’re likely to purchase something while shopping. (Not all this work was conducted with Liquid Ass; some studies used another type of novelty fart spray.)

Scientists working in this field hope to understand what factors may lead a person to be more prone to feeling disgust, even in the absence of anything biologically disgusting. If medical professionals can understand how disgust may delay a patient to seek treatment for a condition that affects the bowels, perhaps they can find ways to communicate with patients to encourage them to come in sooner. As training with Liquid Ass has shown, it is possible to overcome the instinctual feeling.

Wittman and Masters never thought they’d be answering these medical and psychological questions. “When we went into this, it was strictly pranks because that’s what we were doing,” Wittman says. “The fact that it expanded is something we never imagined.”

Correction (July 10): An earlier version of this story misstated the company’s name as Liquid Ass, LLC. It is actually Liquid Ass Novelties, LLC. In addition, the company’s product comes in 1 oz bottles, not 3 oz bottles.