What is alcohol intolerance?

Alcohol intolerance is an inherited metabolic disorder. With alcohol intolerance, drinking just small or moderate amounts of alcohol (ethanol) causes unpleasant sensations. This metabolic disorder affects the enzyme that regulates alcohol metabolism.

Alcohol flushing syndrome is a typical reaction. The skin on your face, neck and chest may become red and warm immediately or soon after you drink alcohol. People of Japanese, Chinese or Korean ethnic groups are most likely to experience this reaction. For that reason, the syndrome is known as Asian glow or Asian flush.

Sensitivity to alcohol may occur due to allergic reactions to various compounds found in alcoholic beverages. This is somewhat different from alcohol intolerance. Sulfites used as preservatives in food or wine may cause an allergic response. Certain medications can also increase sensitivity to alcohol.

Alcohol intolerance is not the same as intoxication. People who are alcohol-intolerant are not more likely to become drunk after drinking small quantities of alcohol. Their metabolic condition does not increase blood alcohol levels. In fact, the unpleasant reactions associated with drinking may serve to deter heavy drinking.

What are the causes of alcohol intolerance?

Alcohol intolerance is usually caused by a genetic metabolic disorder. Enzymes (proteins that control the breakdown of foods) are less active or inactive due to the mutation. When you drink alcohol (ethanol or ethyl alcohol), the liver converts it to acetaldehyde. The alcohol dehydrogenase (ADH) enzyme controls the metabolism of ethanol. Another enzyme called aldehyde dehydrogenase 2 (ALDH2) regulates the conversion of acetaldehyde, a harmful substance, to acetic acid (vinegar), a nontoxic byproduct.

In many cases, people who are alcohol-intolerant have a genetic mutation that makes the ALDH2 enzyme less active or inactive. This means that the acetaldehyde cannot be efficiently converted to acetic acid and it starts to build up in the blood and tissues.

Unless it is converted to acetic acid, acetaldehyde continues to accumulate in the body. Too much of it causes the skin to flush. Acetaldehyde also causes the release of histamines that lead to inflammation. It may cause nausea and a rapid heartbeat.

What are the symptoms of alcohol intolerance?

The most common and characteristic symptoms of alcohol intolerance include:

  • Facial flushing, where skin on the face, neck, and chest appears red and warm.
  • Nausea.
  • Rapid heartbeat (tachycardia) or heart palpitations.
  • Hypotension (lowered blood pressure).
  • Throbbing headache.
  • Hangover-like symptoms (headache, fatigue).

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