Alcohol Intolerance: Symptoms, Causes & Testing

Written by Abby Doty

& Medically Reviewed by Benjamin Caleb Williams, RN

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If you experience uncomfortable symptoms when drinking alcohol, you may have an intolerance to alcohol. Your genetics or medication may play a role.

Alcohol intolerance is a condition that causes unpleasant symptoms whenever you drink alcohol. This can cause discomfort and make certain social situations challenging. Understanding the symptoms, causes and available testing can help you navigate this condition more effectively. 

What Is Alcohol Intolerance?

Alcohol intolerance inhibits the body’s ability to break down alcohol efficiently, leading to undesirable reactions whenever you use alcohol. This condition can cause a range of uncomfortable symptoms, but it is best known for producing facial flushing and hangover-like symptoms.

Alcohol Allergy vs. Intolerance

Alcohol allergy and alcohol intolerance are frequently confused or used interchangeably; however, they are very different from each other. Understanding the differences between the two is important, as it significantly changes how they are managed.

An alcohol allergy happens when your immune system responds to something in an alcoholic beverage. This is rarely the alcohol; more commonly, it is another ingredient in the beverage. Alcohol intolerance is not a reaction to alcohol but occurs because your body can’t break down alcohol properly, resulting in a build-up of an irritating chemical called acetaldehyde.

Causes of Alcohol Intolerance

Alcohol intolerance is primarily caused by a deficiency in an enzyme called aldehyde dehydrogenase (ALDH2). This enzyme is crucial for breaking down alcohol into chemicals the body can easily eliminate. Genetic factors play a significant role in determining whether you have this enzyme deficiency, and it is more prevalent in individuals of East Asian descent.

How Does Sudden Onset Alcohol Intolerance Occur?

Sometimes, alcohol intolerance can begin suddenly. If this is truly alcohol intolerance and not alcohol allergy, it is often due to medications. Metronidazole (an antibiotic) or disulfiram (an alcohol abuse deterrent) are two medications that can cause this reaction.

Sudden onset alcohol intolerance can also occur due to changes in your body, such as certain cancers or hormonal imbalances. While this is rarely the reason for the sudden development of alcohol intolerance, it can be a potential cause.

Symptoms of Alcohol Intolerance

If you have alcohol intolerance, you may experience a range of symptoms. These will typically begin almost immediately after consuming alcohol and include:

  • Flushing of the skin, especially the face
  • Nasal congestion
  • Elevated heart rate
  • Nausea and vomiting
  • Headaches

These symptoms may be uncomfortable, and someone with alcohol intolerance can only avoid it by abstaining from alcohol.

Alcohol Intolerance Testing

If you suspect you have alcohol intolerance, you should see a doctor for a diagnosis. Typically, the condition will be diagnosed by ruling out an alcohol allergy and evaluating the presence of alcohol intolerance symptoms whenever alcohol is used. Genetic testing can sometimes be used to determine whether you have the genes that can cause alcohol intolerance.

Can Alcohol Intolerance Be Treated?

Unfortunately, there is no cure for genetic alcohol intolerance. The most effective treatment is avoiding alcohol. If your alcohol tolerance has another cause beyond your genetics, treating the reason or stopping medications that cause it may help.

The symptoms of alcohol intolerance can be managed; however, the frequent build-up of acetaldehyde in your bloodstream increases your risk of cancer and other health risks. Ultimately, you should avoid using alcohol if you have an alcohol intolerance.


MedlinePlus. “Alcohol.” March 22, 2022. Accessed September 29, 2023.

Morozova, Tatiana V.; Mackay, Trudy F. C.; & Anholt, Robert R. H. “Genetics and genomics of alcohol sensitivity.” Molecular Genetics and Genomics, 2014. Accessed September 29, 2023.

Zhang, Wei Sen; Jiang, Chao Qiang; & et al. “Alcohol sensitivity, alcohol use and hypertension in an older Chinese population: the Guangzhou Biobank Cohort Study.” Hypertension Research, June 26, 2009. Accessed September 29, 2023.

Mergenhagen, Kari A. & Wattengel, Bethany A. “Fact versus Fiction: a Review of the Evidence behind Alcohol and Antibiotic Interactions.” Antimicrobial Agents and Chemotherapy, March 2020. Accessed September 29, 2023.

Genetic and Rare Diseases Information Center. “Acute alcohol sensitivity.” February 2023. Accessed September 29,  2023.


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