ALDH2 rs671: the alcohol flush variant
If your face goes red, your heart races, and you feel queasy after a single drink, there's a good chance you carry ALDH2 rs671 — the variant behind the "alcohol flush reaction" (sometimes called "Asian glow"). Here's what it is, how to find it in your 23andMe or AncestryDNA raw data, and why it's more than a cosmetic quirk.
What ALDH2 does
When you drink alcohol, your body converts it to acetaldehyde — a toxic, carcinogenic compound — and then the enzyme ALDH2 (aldehyde dehydrogenase 2) breaks acetaldehyde down into harmless acetate.
The rs671 variant (Glu504Lys) changes one amino acid and largely inactivates the enzyme:
- G allele (the *1 version): normal, active enzyme.
- A allele (the *2 version): inactive enzyme — acetaldehyde accumulates.
What the genotypes are associated with
| Genotype | Enzyme | Associated effect |
|---|---|---|
| GG | Fully active | Normal alcohol processing, no flush from this variant |
| GA | Reduced | Noticeable flushing, faster heartbeat, lower tolerance |
| AA | Largely inactive | Strong flushing, nausea, very low alcohol tolerance |
The A allele is most common in people of East Asian descent. Beyond the visible flush, it matters for health: because acetaldehyde is a carcinogen, carriers who drink regularly have an elevated risk of esophageal and head/neck cancers. That's a genuine reason some carriers choose to drink little or not at all.
How to find rs671 in your raw data
- Download your raw data (or from AncestryDNA / MyHeritage).
- Search it for
rs671and read your genotype. - Or use our free DNA explorer — it reads your file in your browser, nothing uploaded.
Strand note: 23andMe typically reports rs671 on the G/A strand (A = the flush-causing allele).
What it does and doesn't tell you
ALDH2 status is one of the clearer gene-to-trait links in consumer genetics — if you flush, you likely carry it. But the cancer-risk association is about alcohol intake, and this page is educational, not medical advice. If you carry the A allele and drink, that's worth raising with a clinician.
For the full picture of your file, see our complete guide to analyzing 23andMe raw data, or browse the rest of the Quanome blog.
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Frequently asked questions
What does ALDH2 rs671 cause?
ALDH2 breaks down acetaldehyde, a toxic byproduct of alcohol. The rs671 A allele produces an inactive enzyme, so acetaldehyde builds up — causing facial flushing, rapid heartbeat, and nausea after drinking (the 'alcohol flush reaction' or 'Asian glow').
Which ALDH2 genotype causes flushing?
GG is the normal, fully active form. GA (one A allele) causes reduced enzyme activity and noticeable flushing. AA causes severe deficiency, strong flushing, and very low alcohol tolerance. The A allele is most common in people of East Asian descent.
How do I find ALDH2 rs671 in my raw data?
Search your raw DNA file for rs671 and read the two-letter genotype, or use a tool that looks it up. 23andMe typically reports this marker on the G/A strand.
Is the alcohol flush reaction dangerous?
It can be relevant: carriers who drink regularly have a higher risk of esophageal and other cancers because acetaldehyde is a carcinogen. This is educational, not medical advice — discuss your own risk with a clinician.
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