This Rare Condition Makes Some People Get Drunk, Even When They Haven’t Touched a Drop of Alcohol

In April 2022, police pulled over a brewery worker in Belgium and found that his blood alcohol level was more than four times the legal limit. He was pulled over again about a month later, with a blood alcohol level more than three times the legal limit.

The most logical explanation? Both times, he’d had too much to drink and decided to get behind the wheel anyway. But that story has one big problem: In each instance, the man hadn’t consumed a drop of alcohol.

Instead, the 40-year-old has a rare medical condition that causes his body to produce its own alcohol. Called auto-brewery syndrome, or ABS for short, the unusual disorder can make life difficult for its sufferers—and get them into sticky situations.

The brewery worker was acquitted of drunk driving charges this week, after three doctors who separately examined him confirmed he has ABS. The man’s lawyer, Anse Ghesquiere, said it was an “unfortunate coincidence” that he worked at a brewery, per Reuters.

In the verdict, the judge noted that even though the man had high levels of alcohol in his body, he did not experience symptoms of intoxication. This is not uncommon among people with ABS, some of whom can tolerate blood alcohol levels that would seriously sicken or even kill others.

“They can function at alcohol levels such as 0.30 and 0.40, when the average person would be comatose or dying,” said Barbara Cordell, a retired dean of nursing at Panola College who founded the nonprofit Auto-Brewery Syndrome Information and Research, to CNN’s Sandee LaMotte in 2016. “Part of the mystery of this syndrome is how they can have these extremely high levels and still be walking around and talking.”

ABS works like this: When a patient eats food that contains carbohydrates, their gut bacteria and fungi convert the sugars into carbon dioxide and alcohol. This process, known as fermentation, is how beer, wine, mead, hard cider and other types of alcoholic beverages are made—it just happens to be taking place inside a person’s body, instead of in tanks at a brewery or winery.

In two very rare instances, fermentation occurred in one patient’s bladder and in another patient’s mouth, write Cordell and two other researchers in an article shared by the National Library of Medicine.

Small amounts of fermentation occur during normal digestion, but with ABS, gut microbes become harmful pathogens. This extreme fermentation can make some patients show signs of intoxication, even when they haven’t had an alcoholic drink.

People are typically not born with ABS, but they may develop it later in life—especially if they already have other health issues, such as obesity, diabetes or Crohn’s disease. Antibiotics can also disrupt the balance of a person’s gut microbiome.

Patients can often manage the condition by limiting their consumption of high-carbohydrate foods and taking probiotics. In some chronic cases, a doctor may prescribe fecal transplants—that is, a procedure that involves collecting healthy gut bacteria from a donor and transferring them to the patient’s colon.

ABS is “probably underdiagnosed,” the trio of researchers write, but the condition occasionally makes headlines. In December 2014, for instance, a man was driving a tanker truck full of salmon in Oregon when he crashed and spilled the fish all over the highway. His blood alcohol level was more than three times the legal limit, and he was convicted of a DUI. But later, he appealed the decision and claimed to have ABS.

In 2019, doctors published a case report on a 46-year-old man who’d started suffering from depression, brain fog and mental changes after taking antibiotics. Under the supervision of a medical team, he ate a carbohydrate-heavy meal, which caused his blood alcohol level to rise. Weeks later, his condition caused him to fall and get admitted to a hospital, where his blood alcohol level hit 0.40—high enough to cause coma or death.

Another man, Mark Mongiardo, lost his teaching and coaching jobs before being diagnosed with the condition. He shared his story publicly in hopes that “if I could help others understand that this is out there, maybe someone won’t have to go through the same thing I went through,” he told TODAY’s Meghan Holohan last year.

“It’s devastating for someone to live with this,” he added.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.