Auto-Brewery Syndrome Explained

Medically Reviewed By Cynthia Taylor Chavoustie, MPAS, PA-C
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Auto-brewery syndrome is a rare condition in which fungi or bacteria produce ethanol inside the body. People with this condition display symptoms of inebriation despite not drinking alcohol.  Adults and children with auto-brewery syndrome produce ethanol in their gastrointestinal system, oral cavity, or urinary system. Doctors refer to this internal process as endogenous fermentation and sometimes call the condition “gut fermentation.” 

There are fewer than 100 reported cases of auto-brewery syndrome worldwide. However, some researchers believe it is underdiagnosed. While auto-brewery syndrome can negatively affect a person’s ability to function daily, the condition is treatable.

Learn more about the symptoms, causes, and treatments of this condition. 

What are the symptoms of auto-brewery syndrome?

Unseen person's arm holding very small beer in palm of hand against bright blue background
Studio Firma/Stocksy United

People with auto-brewery syndrome experience elevated blood alcohol content despite drinking little or no alcohol. They also display outward symptoms of drunkenness, such as: 

Other symptoms include: 

Learn about 10 common digestive disorders here.

What causes auto-brewery syndrome?

Auto-brewery syndrome occurs when yeast or bacteria over-colonize and produce ethanol. However, yeast-related cases are more common. A surplus of the following yeasts and bacteria may initiate the fermentation process: 

  • Saccharomyces cerevisiae
  • Saccharomyces boulardii
  • Candida glabrata
  • Candida albicans
  • Candida kefyr
  • Candida parapsilosis
  • Klebsiella pneumonia
  • Enterococcus faecium 
  • Enterococcus faecalis
  • Citrobacter freundii

Risk factors

A disturbance in the gut, oral, or urinary microbiome or mycobiome causes this condition. An underlying health condition or external factor can lead to the disturbance. 

For example, auto-brewery syndrome more commonly occurs alongside obesity or Crohn’s disease. Additionally, conditions such as type 2 diabetes and liver cirrhosis may increase the blood alcohol concentration levels in people with the condition. 

In a study published in 2021, researchers compared a group of patients with auto-brewery syndrome with a group of participants in the American Gut Project. Those in the group with auto-brewery syndrome were more likely to own a pet, cook at home more often, get less sleep, and have a poorer quality of bowel movements. They also consumed more water but less caffeine, dairy, and candy. 

Another study by the same researchers surveyed people with auto-brewery syndrome and people who were asymptomatic. In this study, the researchers also found that those with auto-brewery syndrome reported using antibiotics for longer periods of time and were more likely to have a diagnosed gastrointestinal disorder. Some medical experts believe antibiotic overuse may be one of the major risk factors. 

Researchers are unsure about whether genetic factors may predispose people to this condition. 

How do doctors diagnose auto-brewery syndrome?

Concerned family members are often the first to bring auto-brewery syndrome cases to a doctor’s attention. People with auto-brewery syndrome often experience brain fog. Due to this, a healthcare professional may ask to speak with the person’s family or friends to gather important information, such as:

  • how often the person takes antibiotics
  • when they last consumed alcohol
  • when their symptoms began

A doctor may also ask questions to determine if a person could be drinking in private due to an alcohol use disorder. 

If your doctor suspects that you have auto-brewery syndrome, they will order laboratory tests to confirm it and test your blood alcohol levels when the symptoms are present. They may suggest you purchase a breathalyzer to log your blood alcohol content in the morning and evening and when symptoms appear. 

Next, they may perform the following tests:

  • complete blood count
  • comprehensive metabolic panel
  • stool test

This testing helps rule out conditions with similar symptoms, such as diabetes and leukopenia, which interfere with the body’s ability to fight infection. 

Your doctor may order further testing before treating you for auto-brewery syndrome. First, they may conduct an endoscopy to view your gut and obtain secretion samples to test for yeast and bacteria. This can help identify the type of yeast or bacteria strain that is causing the condition. 

The other test that can confirm a positive diagnosis is a carbohydrate challenge. Your breath and blood alcohol levels must be at 0 when your doctor administers this test.

First, your doctor will give you 200 grams of oral glucose and supervise you in an isolation room with no access to alcohol. After ingesting the oral glucose, you are allowed to eat a meal of your choosing. Then, your doctor will measure your blood alcohol levels. If your alcohol levels rise at any point during the test, your doctor will confirm a diagnosis of auto-brewery syndrome, and you can begin treatment. 

Learn 7 things your gastroenterologist wants you to know.

How do you treat auto-brewery syndrome?

Using results from your endoscopy, your doctor may prescribe an antifungal medication that targets the specific yeast strain causing your condition. If a bacterial strain is causing your auto-brewery syndrome, your doctor may suggest using a probiotic such as Lactobacillus acidophilus to recolonize the good bacteria in your body. 

During treatment, you must follow a carbohydrate-free diet. This means you must abstain from: 

  • sugar
  • alcohol
  • whole and refined grains, including bread and pasta
  • fruit
  • beans
  • starchy vegetables

In some cases, treating an underlying condition, such as Crohn’s disease, may be necessary. 

Summary

Auto-brewery syndrome is a rare but possibly underdiagnosed condition that causes inebriation after little to no alcohol consumption. It can affect people of all ages and genders.

This condition occurs when there is too much yeast or bacteria in the body that feeds on starchy, sugary foods, leading to fermentation and alcohol production. 

While auto-brewery syndrome is treatable, it may take a while for a doctor to reach a diagnosis. Asking your friends and family for help may speed up the process. A carbohydrate challenge is usually the final test before a positive diagnosis. Your doctor can prescribe antifungal medication or probiotics depending on which bacteria or yeast is causing the fermentation.

During treatment, you will need to avoid all carbohydrates. 

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Medical Reviewer: Cynthia Taylor Chavoustie, MPAS, PA-C
Last Review Date: 2022 Jul 28
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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  3. Cordell, B., et al. (2021). Factors in an auto-brewery syndrome group compared to an American Gut Project group: A case-control study. https://f1000research.com/articles/10-457/v1
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