“Asian flush” is a term applied to a genetic disorder that causes some people of Asian descent to grow flush in the face after consuming alcohol. Symptoms of the disorder can be as mild as a light red glow, much like heavy blushing, or as severe as constricted airways and an elevated heart rate. It is estimated as of 2009 that up to half of East Asians — particularly those tracing their heritage to China, Taiwan, Japan, and Korea — have inherited the genetic defect that causes the so-called Asian flush.
There is no cure for the Asian flush, also called the “Asian glow” or the “Asian sensation” in some settings. So long as those affected abstain from the consumption of alcohol, however, there are no symptoms. The flush is caused exclusively by an inability to process alcohol, and poses no other health concerns.
Under normal circumstances, the human body breaks down alcohol through a two-step metabolic process in the liver. Alcohol dehydrogenases enzymes, also known as ADH enzymes, break the alcohol down into acetaldehyde. The body’s aldehyde dehydrogenases enzymes, or ALDH enzymes, then convert that acetaldehyde into acetic acid, which can easily be absorbed and carried out of the body.
People who are affected by the Asian flush typically have a hard time with the second step of the metabolic process. Their ALDH enzymes are either defective, or work very slowly. This causes alcohol in their bodies to only partially break down, leading to an acetaldehyde accumulation in the liver. That build-up is what causes the reddened face characteristic of Asian flush.
The slowed ALDH reaction time is the result of a genetic disorder in nearly all cases. A person with Asian flush carries genes that code for an inactive ALDH enzyme. This means that the person still makes ALDH, but that the enzyme is not capable of metabolizing alcohol, or else does so very ineffectively.
In most people, there are two genes responsible for ALDH and other metabolic enzyme production. It is very common for only one of these genes to be defective. People who have inherited only one defective gene often show mild symptoms of alcohol flush, often no more than a brief reddening of the ordinarily pale Asian complexion, and slight headache. Two defective genes usually cause more extreme alcohol reactions, such as nausea, vein constriction, and airway constriction. Many doctors warn that repeated Asian flush episodes can lead to heart complications, blood pressure problems, or even esophageal cancer, in some cases.
The extent of a person’s symptoms is often as much a factor of genetic defection as it is overall alcohol consumption. Even a person with only one problematic gene may experience a severe reaction if multiple drinks are consumed, particularly within a short period of time. For those who are affected, the only way to avoid symptoms that are, at best, embarrassing and, at worse, quite dangerous is to avoid alcoholic drinks, or else commit to enjoying them only in the strictest moderation.