A condition which, as its name suggests, is most common among people of Asian descent, although it can be found to a lesser extent in individuals from other ethnic backgrounds. The symptoms of Asian Flush are often described as a simple allergy to alcohol, but in fact arise from a genetic defect.

In an unaffected person, any alcohol consumed will first travel to the bloodstream, and then to the liver, where liver cells called hepatocytes will transform the ethanol (alcohol) to a substance called acetaldehyde. This compound will then be converted to acetic acid, with the aid of an enzyme called aldehyde dehydrogenase. These two conversions form the electron carrier NADH, which enters the electron transport chain, resulting in the formation of ATP, the body's primary source of energy.

As many as half of all Asians possess a defective copy of the gene for aldehyde dehydrogenase, which works at a slower rate than the normal gene. This results in a bottleneck effect during the metabolism of alcohol, causing a build-up of acetaldehyde. This build-up causes the manifestation of the symptoms which characterise the Asian flush, including nausea, malaise, headache, and a red face. Although the condition doesn't significantly contribute to a decreased alcohol tolerance, many scientists believe it is responsible for the relatively low incidence of alcohol abuse among Asians, as the onset of these unpleasant symptoms leave them feeling too ill to consume large amounts of alcohol.

The Asian Flush effect has been mimicked by a number of pharmaceutical companies. An example of this is the drug disulfram, better known as Antabuse. Used in the treatment of chronic alcoholics, the drug inhibits the aldehyde dehydrogenase ezyme, resulting in the same symptoms as Asian Flush, which acts as a deterrent against the consumption of alcohol.