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For Some Asians Alcohol Poses Risk of More than Flushing
By Najla Zaidi | 08 Jul, 2025
People of east Asian ancestry are most at risk for alcohol intolerance, but the condition can affect people of all races and ethnicities.
If you have ever drank an alcoholic beverage, you likely already know if you have alcohol intolerance, a hereditary condition that poses serious health risks. “You either get red and feel uncomfortable, or you don’t,” said Alexander Kuo, MD, medical director of Liver Transplantation in the Karsh Division of Gastroenterology and Hepatology at Cedars-Sinai.
The reaction is informally termed “Asian flush” or “Asian glow” due to its frequent occurrence in East Asians, with approximately 30 to 50% of Chinese, Japanese, and Koreans showing characteristic physiological responses to drinking alcohol. The physical reactions include facial flushing, nausea, headaches and a fast heart rate. Additionally, people affected by this condition show more of a reduction in psychomotor functions on alcohol consumption than those without.
Many cases of alcohol-induced respiratory reactions, which involve rhinitis and worsening of asthma, develop within 1–60 minutes of drinking alcohol and are due to the same causes as flush reactions. These reactions can lead to major health problems, including cancers of the mouth, throat, esophagus, stomach and liver. Asian flush may be also highly prevalent in some Southeast Asian and Inuit populations.
The Asian glow is not simply a reason for embarrassment or social anxiety, but rather is based in science and genetics. This reaction is due to a deficiency in the enzyme aldehyde dehydrogenase 2 (ALDH2), which is crucial for breaking down acetaldehyde, a toxic byproduct of alcohol metabolism. This buildup of acetaldehyde is what causes the flushing, nausea, and other unpleasant symptoms. The genetic variant associated with this reaction also significantly increases the risk of certain health issues, particularly esophageal cancer, for those who consume alcohol regularly.
The ALDH2 gene gives directions for making the enzyme aldehyde dehydrogenase 2, which is responsible for detoxifying acetaldehyde. A common genetic mutation, ALDH2*2, results in a less active or inactive form of the ALDH2 enzyme. Around 20–30% of East Asians carry the rs671 (ALDH2*2) allele on chromosome 12, which results in a less functional acetaldehyde dehydrogenase enzyme, responsible for the breakdown of acetaldehyde, and accounts for most incidents of alcohol flush reaction worldwide. An analysis by the HapMap project indicates, 20% to 30% of people of Chinese, Japanese, and Korean ancestry have at least one ALDH2*2 allele, while it is rare among Europeans and sub-Saharan Africans.
The rs671 allele is native to East Asia and most common in southeastern China. Researchers believe that the rise and spread of rice cultivation in South China correlates with the spread of the allele. The reasons for this positive selection are not known, but it has been hypothesized that higher concentrations of acetaldehyde may have given protection against certain parasitic infections, such as Entamoeba histolytica.
Additionally, in around 80% of East Asians, the rapid accumulation of acetaldehyde is worsened by another gene variant; in this case the allele ADH1B*2. This results in the alcohol dehydrogenase enzyme converting alcohol to toxic acetaldehyde more quickly than other gene variants outside East Asia. Since alcohol is broken down faster, you might experience little to no alcohol “buzz”. However, this also means that the by-product acetaldehyde takes a much longer to clear your bloodstream.
People with reactions due to ALDH2 deficiency may be homozygotes, with two alleles of low activity, or heterozygotes, with one low-activity and one normal allele. Homozygotes find consuming large quantities of alcohol to be so unbearable that they are generally protected from esophageal cancer, but heterozygotes can continue drinking. However, an ALDH2-deficient drinker has four to eight times the risk of developing esophageal cancer as a drinker not deficient in the enzyme.
ALDH2-deficient individuals are at much higher risk for squamous cell carcinoma from alcohol consumption than individuals with fully active ALDH2 according to the National Institute of Health (NIH). This is particularly serious as esophageal cancer is one of the deadliest cancers worldwide, with five-year survival rates of 15.6% in the United States, 12.3% in Europe, and 31.6% in Japan.
It is estimated that there are at least 540 million ALDH2-deficient individuals in the world, representing approximately 8% of the population. In a population of this size, even a small reduction in the incidence of esophageal cancer could result in a substantial reduction in esophageal cancer deaths worldwide.
In the presence of alcohol, the ALDH2 deficient gene in human cell cultures and mice also leads to biochemical changes associated with Alzheimer's disease according to studies done at Stanford Medicine. “Understanding the relationship of alcohol and genes linked to Alzheimer's disease will have broad consequences,” said Daria Mochly-Rosen, PhD, professor of chemical and systems biology.
"Our data suggest that alcohol and Alzheimer's disease-prone genes may put humans at greater risk of Alzheimer's onset and progression," she continued. "This is based on our patient-derived cell studies and our animal studies, so an epidemiological study in humans should be carried out in the future."
While some people attempt to treat the symptoms of Asian flush with cold medicines such as antihistamines, these medications do not reduce the critical risks of the condition. If you experience the tell-tale symptoms of alcohol intolerance, be aware that there’s no treatment or cure for the condition and the long-term effects of overlooking the symptoms may be severe.
“There’s an easy way to sidestep all of the negative health consequences of alcohol intolerance,” said Kuo. “Just don’t drink.”
The Asian glow is not simply a reason for embarrassment or social anxiety, but rather is based in science and genetics.
The alcohol flushing response. (photo courtesy of Wikipedia)
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