Alcohol Flush Reaction

The reaction to alcohol, known as "alcohol flush", is caused by a disorder in the hepatic enzyme aldehyde dehydrogenase (ALDH2) impeding it to adequately metabolize acetaldehyde.

When alcohol metabolizes in the liver it first oxidizes to acetaldehyde and then it is converted into acetate by ALDH2. The persons who have a certain facial flush after drinking a small quantity of alcohol have a genetic change in their ALDH2 which causes the body to metabolize alcohol more quickly, but the decomposition of acetaldehyde is less efficient. Acetaldehyde accumulation makes the blood vessels dilate and the skin turns reddish. This reaction happens especially in the Asian populations and is also known as the "Asian flush" or "Asian glow".

Recent studies have shown that those individuals with an ALDH2 deficiency have also been associated with a greater risk for esophageal cancer and high blood pressure. Acetaldehyde is a byproduct of alcohol metabolism but it is also a carcinogen and mutagen with recognized enabling properties directly related to cancer. When the digestive tract is repeatedly exposed to acetaldehyde, the probability of damage in the DNA and of mutation can increase.

There is a very clear distinction between an alcohol flush and alcohol allergy. The flush reaction is not an allergic reaction although the symptoms can seem similar. The reasons for each reaction are quite different and therefore should be treated differently.

An allergy is an erroneous reaction committed by our body when faced by apparently innocuous substances which the body perceives as prejudicial.

The flush reaction to alcohol is an incapacity of the body to metabolize alcohol correctly because of a ALDH2 enzyme deficiency, i.e., it is not capable of breaking down the byproduct of alcohol metabolism, a chemical called acetaldehyde. This byproduct is toxic and an accumulation of it in the organism can provoke the characteristic symptom of alcohol flush.


The symptoms include a reddish facial color or flushing, heart palpitations, dry mouth and throat which can be accompanied by nauseas and headaches.


The best way to prevent the flushing reaction is to avoid drinking alcohol.

Gene or region studied

  • ALDH2
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