Alcohol intolerance


Alcohol intolerance is present when even the consumption of small amounts of alcohol causes symptoms that otherwise only occur with higher amounts. This results in a slower degradation of ethanol or its degradation products. The slower breakdown leads to the typical symptoms of alcohol intolerance. These consist of redness, swelling and stomach problems, up to hangover symptoms lasting for days, such as muscle, limb and headaches.


The cause of alcohol intolerance is a disturbed breakdown of ethanol. The degradation of ethanol is carried out in the body by two enzymes. Changes in these enzymes lead to a disordered degradation.

In some cases the changes in these enzymes are genetically determined, especially in Asia many people have an alcohol intolerance which is caused by a change on the genetic level. Other causes of alcohol intolerance are organ damage, such as liver or kidney damage, which impairs the breakdown and excretion of alcohol. In addition, certain drugs, such as antibiotics, can disrupt the breakdown of alcohol in the liver, resulting in reversible alcohol intolerance.

Normally, ethanol is broken down by alcohol dehydrogenase to the toxic acetaldehyde. This is then broken down by the aldehyde dehydrogenase to the non-toxic acetate, which is then excreted. However, if these enzymes are defective, alcohol can only be broken down slowly.

If the enzyme alcohol dehydrogenase is not fully functional, the ethanol is broken down slowly and the blood alcohol level drops only very slowly. The more frequent cause, however, is a functionally impaired aldehyde dehydrogenase. The consequence is a high acetaldehyde level. The toxic acetaldehyde is responsible for the typical “hangover” symptoms. High concentrations of this substance damage the organs.

Which test can be used to detect alcohol intolerance?

In many cases, an alcohol intolerance is determined by the person concerned himself. Even small amounts of alcohol lead to severe symptoms after alcohol consumption. The affected person can then avoid the symptoms by abstaining from alcoholic beverages.

If it is to be tested whether a genetically caused alcohol intolerance is present, there is the possibility of DNA analysis. In this method, the part of the DNA on which the genes for the enzymes that break down alcohol are located is examined. If the genetic variant of alcohol intolerance is present, then changes can be detected in the genes for alcohol or aldehyde dehydrogenase.

Certain changes in the DNA section are known to be responsible for a loss of function of the respective enzyme. If an intolerance exists due to liver or kidney damage, it is necessary to examine the respective organs. For this purpose, the liver and kidney values can be determined by a blood test. Imaging procedures can also be used. In case of abnormalities, it is likely that a damaged organ is causing the alcohol intolerance.