How Some People Get Drunk Without Drinking

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IIt’s possible to become intoxicated without taking a single sip of alcohol – and scientists think they’re close to fully understanding why.

Due to a rare condition called auto-brewery syndrome, or ABS, some people’s bodies produce enough ethanol to cause poisoning. It is the same substance found in wine, beer and other types of alcoholic beverages.

In people with ABS, microbes in the gut break down carbohydrates and turn them into large amounts of ethanol that end up in the bloodstream. In most people, this process produces tiny concentrations of alcohol that have no effect. Scientists aren’t sure exactly how this phenomenon occurs, and limited research so far includes case reports on individual patients and a small study of five patients published in 2023.

Fewer than 100 cases of ABS have been recorded worldwide, but researchers suspect the disease is underdiagnosed. This comes with stigma, for example, because patients may be wrongly labeled as drinkers who hide their habits. And diagnosis requires close monitoring to exclude alcohol consumption and detailed blood alcohol monitoring. These tests can be difficult to access and may not be covered by insurance.

“Auto-brewery syndrome is a poorly understood disease with few tests and treatments,” Elizabeth Hohmann, a physician at Mass General Brigham Department of Medicine, said in a statement.

People with ABS can face arrest, face family conflict and other serious consequences, case studies show. This disease can also lead to medical problems such as cognitive impairment, liver damage, and withdrawal symptoms.

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Researchers suspect that an imbalance of gut microbes is to blame and that this condition may be linked to gastrointestinal illnesses such as Crohn’s disease and short bowel syndrome. Some case reports have identified types of ethanol-producing bacteria called Klebsiella in samples from patients with ABS, who recovered with antibiotics. But the precise causes of this mysterious condition remain elusive.

To learn more about the triggers and treatments for ABS, Hohmann and colleagues examined the composition of the gut microbes of 22 people diagnosed with the condition, as well as 21 unaffected people from their households, to see if their environment and diet play a role. The study, published today in Natural microbiologyalso included 22 healthy control participants.

Stool samples and blood tests revealed that during a flare-up, median ethanol concentrations in ABS patients were significantly higher, almost three times higher, than those seen in family partners. This suggests that ABS could be diagnosed by a stool test, which could prove a much more convenient and accessible option than the other testing methods described above.

Those who suffered from ABS also had higher amounts of bacteria such as Escherichia coli And Klebsiella pneumoniae in their stools. These microbes are known to transform sugars into alcohol. Previously, research had suggested that certain fungi were to blame. But overall, the precise types of tiny criminals behind ABS are still unclear, and it’s difficult to determine all the species involved.

Scientists also noticed that during flares, some ABS patients had elevated levels of certain enzymes known to be involved in fermentation. “The authors note that rather than focusing on specific bacterial species, treatments targeting microbial enzymes involved in ethanol production may be a more effective strategy,” according to the release.

The study looked at the results of a person with ABS who also received a fecal transplant containing healthy bacteria. During remission, the composition of the microbes in his gut had changed to mirror those of the donor. And after a second transplant, the patient had no symptoms for more than 16 months. Hohmann’s team is currently working on a phase 1 clinical trial testing this type of graft in eight patients with ABS.

“Our findings could pave the way for easier diagnosis, better treatments and better quality of life for people living with this rare disease,” Hohmann said.

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Main image: Dirk Wohlrabe / Pixabay

• Molly Glick

  Published on January 8, 2026

  Molly Glick is the newsletter editor of Nautilus.