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Alcohol Intolerance: Symptoms, Causes and Treatment

Written by Theresa Valenzky

& Medically Reviewed by Benjamin Caleb Williams, RN

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Medically Reviewed by Benjamin Caleb Williams, RN

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Updated 09/13/2023

Alcohol intolerance has several side effects when someone drinks, like abdominal pain and nausea. Recognizing the difference between these and an alcohol allergy could save a life.

What Is Alcohol Intolerance?

Alcohol intolerance, also known as alcohol sensitivity, is often caused by a change that affects an enzyme called alcohol dehydrogenase. This enzyme is part of the body’s process for breaking down alcohol and changes a chemical called acetaldehyde to another chemical called acetate. The change caused by alcohol intolerance makes it impossible for the body to break down acetaldehyde as it should, causing this chemical to build up in the body.

What Causes Alcohol Intolerance?

Alcohol intolerance can be caused by anything that affects the function of alcohol dehydrogenase. Incorrect function in alcohol dehydrogenase enzymes can be caused by factors including:

  • Genetic changes
  • Chemical changes
  • Heredity

Genetic Alcohol Intolerance

Genetic alcohol intolerance is inherited from one’s parents and caused by a mutation in the gene that the body uses to create alcohol dehydrogenase. This condition is most common in those of Asian descent but can affect anyone, regardless of their ethnic background. This genetic condition will cause alcohol intolerance throughout a person’s life.

Alcohol Intolerance as a Result of Disease

Certain diseases can affect how well alcohol dehydrogenase functions. Some conditions can cause a sudden onset of alcohol intolerance in those who have never had difficulty drinking, including:

Alcohol intolerance with these conditions is rare but can occur. The sudden development of alcohol intolerance does not always mean a new disease is present. However, a person in this situation should still seek medical attention to ensure a health problem has not developed.

Alcohol Intolerance as a Result of Medications

Certain medications can create alcohol intolerance by inhibiting the action of alcohol dehydrogenase. The most common medicines that create this side effect include: 

  • Metronidazole (Flagyl): This is a commonly used antibiotic. 
  • Disulfiram (Antabuse): This drug creates alcohol intolerance to deter alcohol use in people struggling with alcohol addiction.

Symptoms of Alcohol Intolerance

The main symptom of alcohol intolerance is sudden flushing in the face. Often, alcohol intolerance also causes a stuffy nose and symptoms similar to a hangover. Common symptoms of alcohol intolerance include:

  • Redness in the face
  • Stuffy or runny nose
  • Hot flashes
  • Abdominal pain
  • Nausea or vomiting
  • Diarrhea
  • Headaches

Alcohol Allergy vs. Intolerance

Alcohol intolerance is not the same as an alcohol allergy. While both conditions lead to unpleasant symptoms after using alcohol, the cause of these symptoms is very different. 

Alcohol intolerance is due to the buildup of acetaldehyde, which is caused by a problem affecting alcohol dehydrogenase. Alcohol intolerance symptoms are unpleasant but rarely actually dangerous.

However, alcohol allergy occurs when someone’s immune system reacts to alcohol, causing the body to attack it. Although most alcohol allergies are due to a reaction to a component of the alcohol, such as grapes, hops or wheat, instead of the alcohol itself, alcohol allergy symptoms can range from mildly unpleasant to life-threatening. Mild symptoms include rash, but more dangerous symptoms include swelling in the face and throat, which can affect the ability to breathe. If you suspect you or someone you know is having a severe allergic reaction, immediately call 911.

Alcohol Intolerance Test

Alcohol allergy can be diagnosed using allergy testing specifically for alcohol and the sources that alcohol often comes from. Alcohol intolerance, however, is more difficult to test for. Physicians often diagnose alcohol intolerance based on symptoms and the fact that the symptoms develop right after drinking alcohol. Doctors also tend to rule out alcohol allergy before diagnosing alcohol intolerance. Genetic tests can also evaluate if there are problems with the genes that make alcohol dehydrogenase. However, this is not always the cause of alcohol intolerance.

Alcohol Intolerance Treatment

Treating alcohol intolerance depends on its cause. If alcohol intolerance is due to a disease or medication use, successfully treating that disease or stopping the medication will often help resolve alcohol intolerance. If alcohol intolerance is due to genetic causes, then no treatment will make it go away. Stopping alcohol use will be the only way to avoid alcohol intolerance symptoms.

Though alcohol intolerance is typically untreatable, there may be ways to reduce the symptoms that will inevitably occur when using alcohol, including: 

  • Using medications to treat the symptoms that are particular to each person. 
  • Discouraging drinking in those with alcohol intolerance, as the buildup of acetaldehyde can increase the risk of cancer and other serious health problems.

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