Why do I get red when I drink?
Usually because of a gene variant that slows an enzyme called ALDH2. Your body turns alcohol into acetaldehyde, a toxic chemical, and ALDH2 is what clears it. When ALDH2 is slow, acetaldehyde builds up and your face and neck turn red. About 36% of East Asians flush.
The flush gets called the “Asian glow”, treated as a funny quirk, mistaken for an allergy, or written off as something you grow out of with practice. It’s a sign that a toxic chemical is building up in your body faster than you can clear it, and it’s tied to a much higher cancer risk in people who keep drinking anyway.
What we’d do
Take the flush as a reason to drink less, or not at all. People with the variant who drink have a much higher risk of esophageal cancer than other people who drink the same amount. Don’t try to drink through it, because the people who get used to the flush and keep drinking are the ones with the highest risk.
Why it happens
Clearing alcohol takes two steps, like two toll booths in a row. The first booth turns alcohol into acetaldehyde, and the second, ALDH2, turns acetaldehyde into acetate, which the body uses as fuel. If the second booth is nearly closed, traffic backs up between them, and the backed-up acetaldehyde is what makes you flush, along with nausea and a racing heart.
A 2009 paper led by researchers at NIAAA explains the gene. One version of ALDH2 makes an enzyme that doesn’t work at all. People with two copies have no measurable ALDH2 activity, and people with one copy have more than 100 times less activity than people without it. The paper estimates at least 540 million people carry the variant, about 8% of the world, mostly people of Japanese, Chinese and Korean descent.
Why the flush is a cancer warning
Acetaldehyde damages DNA. NCI calls it a toxic chemical and a probable human carcinogen, and says people with the slow form of ALDH2 who drink even moderate amounts have a higher risk of esophageal and head and neck cancers than people with the normal enzyme who drink similar amounts. Those higher risks don’t show up in carriers who don’t drink.
The 2009 paper gives the size. In case-control studies in Japan and Taiwan, people with one copy of the variant who drank had 3.7 to 18.1 times the odds of esophageal cancer after taking the amount they drank into account, and most studies found more than 10 times the odds in heavy drinkers.
The paradox of getting used to it
The flush is unpleasant enough that most people with the variant drink little, according to NCI. But people with one copy flush less strongly than people with two, and the 2009 paper says some of them get used to the flush and become heavy drinkers. They’re the group with the highest risk of esophageal cancer.
The paper also gives a two-question check that doctors can ask, tested in Japanese men: do you flush right after about a glass of beer (about 6 oz), and did you in your first year or two of drinking? A yes to either one picked out about 90% of people with the variant. The second question is there because the flush can fade.
Does alcohol cause cancer? covers the risk for everyone else.
2 sources
- Brooks PJ and others, The alcohol flushing response: an unrecognized risk factor for esophageal cancer from alcohol consumption, PLoS Medicine, 2009journals.plos.org
- National Cancer Institute, Alcohol and Cancer Risk, reviewed May 2, 2025cancer.gov
