Part of our Asian Flush & Alcohol guide library.
Short answer: Asian flush happens mainly because of an inherited variant of the ALDH2 gene, often called ALDH2*2, that is common in East Asian populations and essentially absent elsewhere. The variant makes the ALDH2 enzyme far less able to break down acetaldehyde, a toxic byproduct of alcohol, so acetaldehyde builds up and causes flushing, nausea and a racing heart. About 36% of East Asians (Japanese, Chinese and Koreans) have this flushing response, an estimated 540 million people worldwide.
Why does a glass of beer turn some people bright red while their friends look the same? For most people with Asian flush, the answer is written in their genes. Here is how the ALDH2 variant works, where it came from, and who can have it.
What you'll learn
- How alcohol is broken down, and where the ALDH2 variant changes things
- Why the variant is common in East Asia but rare elsewhere
- Why some people flush more than others
- Whether people who are not Asian can get Asian flush
How your body breaks down alcohol
Alcohol is processed in two main steps (Brooks et al., 2009):
- Alcohol to acetaldehyde. The enzyme alcohol dehydrogenase (ADH) converts ethanol into acetaldehyde, a toxic compound that can damage DNA.
- Acetaldehyde to acetate. The enzyme aldehyde dehydrogenase 2 (ALDH2) then converts acetaldehyde into acetate, which the body can use or clear.
Asian flush happens when step 2 is slow. Acetaldehyde accumulates and causes facial flushing, nausea and a fast heartbeat, partly through effects such as histamine release (Brooks et al., 2009). Alcohol also widens blood vessels in the skin, which adds to the redness and warmth (Cleveland Clinic).
The ALDH2 gene variant
In East Asian populations there are two main versions of the ALDH2 gene. One makes a normal enzyme; the other, often written ALDH2*2 or Glu487Lys, makes an inactive one (Brooks et al., 2009). You inherit one copy of the gene from each parent:
| Your two copies | ALDH2 activity | What it usually means |
|---|---|---|
| Two normal copies | Normal | No ALDH2-related flushing |
| One normal, one variant | Far less than half; reduced more than 100-fold | Flushing, though some people develop tolerance to it over time |
| Two variant copies | No detectable activity | Reactions so unpleasant that most cannot drink significant amounts |
The variant acts as a "dominant negative": a single copy is enough to greatly reduce enzyme activity, which is why one copy causes noticeable symptoms (Li et al., 2009; Brooks et al., 2009).
Why is it common in East Asia?
A study pooling data on more than 80,000 people from 366 population samples found that the ALDH2*2 variant is essentially absent in all parts of the world except East Asia (Li et al., 2009). Within East Asia:
- It is most common in Southeast China, and occurs in most areas of China, Japan, Korea, Mongolia and Indochina, with frequencies gradually declining with distance from Southeast China.
- Because indigenous populations in South China carry it much less often than Han Chinese migrants from Central China, the researchers concluded that the variant spread across East Asia with Han Chinese migration.
Why the variant became so common in the first place is still debated. Researchers have found clearer evidence for a second alcohol gene, described below.
A second gene: ADH1B and the rice connection
Many East Asians also carry a fast-working version of the ADH1B gene, ADH1B*47His, which converts alcohol into acetaldehyde up to 100 times faster than the ancestral version. A faster first step may add to acetaldehyde build-up and flushing (Peng et al., 2010).
In a study of 38 East Asian populations, this variant reached 98.5% in Han Chinese from Zhejiang province but was uncommon in Tibetan populations. It arose roughly 7,000 to 10,000 years ago, and its spread matches the spread of rice farming in East Asia, which the authors propose drove natural selection on the gene (Peng et al., 2010). ADH1B variants also interact with ALDH2 to modify health risks (Brooks et al., 2009).
How many Asians have Asian flush?
Roughly a third or more of East Asians. About 36% of East Asians (Japanese, Chinese and Koreans) show the alcohol flushing response, and researchers estimate there are at least 540 million people with ALDH2 deficiency worldwide, about 8% of the global population (Brooks et al., 2009). Cleveland Clinic puts the figure at about 35% to 45% of East Asians (Cleveland Clinic).
"Asian" covers a huge range of people, though. Because ALDH2*2 is essentially limited to East Asia (Li et al., 2009), people of South Asian ancestry, for example, are much less likely to carry it, and frequency varies even between regions of China.
Can people who are not Asian get Asian flush?
The ALDH2*2 variant is rare outside East Asian populations (Li et al., 2009), but people of any background can flush when they drink for other reasons:
- Rosacea. If someone flushes with alcohol but does not have ALDH2 deficiency, rosacea may be the cause (Cleveland Clinic).
- Medications. Some antibiotics, such as metronidazole and tinidazole, and some older diabetes medications, such as chlorpropamide, can cause a flushing reaction with alcohol (NIAAA).
- Other gene variants. Gene variations that cause flushing, nausea, headaches and a rapid heartbeat when drinking are more common in some populations, including people of Asian or Jewish descent (MedlinePlus Genetics).
For a side-by-side comparison, see our complete guide to Asian flush.
Why it matters for your health
The flush is a visible signal that acetaldehyde is building up. In people with ALDH2 deficiency, regular drinking is linked to a much higher risk of esophageal cancer, while ALDH2 deficiency does not raise that risk in non-drinkers (Brooks et al., 2009). People with one variant copy can become tolerant to the flush and drink more, which is why the more common one-copy group carries the greatest risk from drinking (Brooks et al., 2009).
Hiding the redness with antihistamines does not lower acetaldehyde. See Asian flush pills, Pepcid and patches and how to prevent Asian flush.
Common myths (quick reality check)
Myth: Asian flush is an alcohol allergy. Reality: It is mainly a genetic difference in how you break down acetaldehyde, not an immune reaction.
Myth: You can train your body out of it. Reality: Some people with one variant copy become tolerant to the flush, but their ALDH2 enzyme does not improve, and their health risk from drinking stays higher.
Myth: All Asians get Asian flush. Reality: About a third or more of East Asians do. The ALDH2 variant is essentially absent outside East Asia, so many people of Asian descent do not carry it.
Frequently asked questions (FAQ)
Why do Asians get Asian flush?
Mainly because of an inherited ALDH2 gene variant common in East Asia. It slows the breakdown of acetaldehyde, a toxic byproduct of alcohol, which builds up and causes flushing, nausea and a fast heartbeat.
How many Asians have Asian flush?
About 36% of East Asians (Japanese, Chinese and Koreans) have the alcohol flushing response. Researchers estimate at least 540 million people worldwide have ALDH2 deficiency.
Can white people get Asian flush?
The ALDH2 variant behind Asian flush is rare outside East Asian populations, but anyone can flush after drinking because of rosacea, certain medications, or other gene variants.
Is Asian flush genetic?
Yes. It is mainly caused by an inherited variant of the ALDH2 gene. One copy greatly reduces enzyme activity; two copies leave no detectable activity.
Why does Asian flush happen with even one drink?
With the ALDH2 variant, even small amounts of alcohol produce acetaldehyde faster than your body can clear it, so flushing can start soon after a single drink.
Related guides
- Is Asian flush dangerous? What it means for your health
- Alcohol intolerance vs alcohol allergy vs Asian flush
- Asian flush (Asian glow): causes, risks and how to reduce it
- How to prevent Asian flush: a before-you-drink checklist
- Asian flush pills, Pepcid and patches: does anything work?
- Alcohol and liver disease: the complete guide
Disclaimer and when to seek help
This article is for general education and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease. Talk to a health care provider if you flush strongly when you drink, take medications that may interact with alcohol, or are unsure whether drinking is safe for you. Seek emergency care right away for trouble breathing, swelling of the face, lips or throat, widespread hives, chest pain, or fainting after drinking.
References
- Brooks PJ, Enoch MA, Goldman D, Li TK, Yokoyama A. "The alcohol flushing response: an unrecognized risk factor for esophageal cancer from alcohol consumption." PLoS Medicine, 2009;6(3):e1000050. doi:10.1371/journal.pmed.1000050
- Li H, et al. "Refined geographic distribution of the oriental ALDH2*504Lys (nee 487Lys) variant." Annals of Human Genetics, 2009;73(Pt 3):335-345. doi:10.1111/j.1469-1809.2009.00517.x
- Peng Y, et al. "The ADH1B Arg47His polymorphism in East Asian populations and expansion of rice domestication in history." BMC Evolutionary Biology, 2010;10:15. doi:10.1186/1471-2148-10-15
- Cleveland Clinic Health Essentials. "Here's Why You Get an Alcohol Flush Reaction Every Time You Drink". July 16, 2025.
- National Institute on Alcohol Abuse and Alcoholism (NIAAA). "Harmful Interactions: Mixing Alcohol with Medicines".
- MedlinePlus Genetics (U.S. National Library of Medicine). "Alcohol use disorder".
