If you turn red after a drink or two, there's a good chance ALDH2 deficiency is the reason. It's one of the most common genetic variants in the world, yet most people who have it have never heard the name.

Here's what it actually means — and what you can do about it.

What Is ALDH2?

ALDH2 stands for aldehyde dehydrogenase 2. It's an enzyme produced in your liver, and its job is to break down acetaldehyde — a toxic compound your body creates when it metabolises alcohol.

In most people, this process happens quickly. Alcohol converts to acetaldehyde, ALDH2 converts acetaldehyde into harmless acetic acid, and the whole thing clears within minutes. You might feel a little warm. Nothing dramatic.

In people with ALDH2 deficiency, that second step is broken. Acetaldehyde builds up in the bloodstream instead of being cleared — and that buildup is what causes the flushing, the racing heart, the nausea, and the headaches that come with Asian flush.

Who Has ALDH2 Deficiency?

It's predominantly found in people of East Asian descent — Chinese, Japanese, Korean, Vietnamese, and other related populations. Estimates suggest roughly 30 to 40 percent of East Asians carry some form of the variant, making it one of the most widespread genetic differences in human metabolism.

The condition exists on a spectrum. Some people inherit one copy of the variant gene (heterozygous), which means their ALDH2 enzyme is partially functional — they flush, but it's manageable. Others inherit two copies (homozygous), and their ALDH2 barely works at all. Those people typically flush severely even from very small amounts of alcohol.

It's not exclusively an Asian condition, though the name "Asian flush" has stuck. People of other ethnic backgrounds can also carry ALDH2 variants, just at much lower rates.

Why Acetaldehyde Buildup Matters

Acetaldehyde isn't just uncomfortable. It's classified by the International Agency for Research on Cancer as a Group 1 carcinogen — the same category as tobacco smoke. People with ALDH2 deficiency who drink regularly are exposed to far higher concentrations of acetaldehyde than the general population, for longer periods of time.

The visible symptoms — redness, flushing, racing pulse — are your body signalling that something toxic is circulating at levels it can't clear. That signal is worth paying attention to, not masking.

Can You Test for It?

Yes. Consumer DNA testing services like 23andMe include ALDH2 variant reporting as part of their health results. If you already know you flush consistently, the test will almost certainly confirm what your body has been telling you. Where it becomes more useful is understanding severity — whether you have one or two copies of the variant, which affects how your body handles alcohol.

What ALDH2 Deficiency Means in Practice

Having ALDH2 deficiency doesn't mean you can't drink. It means drinking comes with a higher exposure to acetaldehyde than it does for most people, and that exposure carries real long-term implications if it goes unmanaged.

The most effective approaches focus on reducing acetaldehyde buildup — not just hiding the symptom of redness. Drinking less and more slowly helps. Eating before drinking helps. Choosing lower-ABV options helps. And purpose-built supplements that support acetaldehyde clearance can make a meaningful difference to how your body handles alcohol at a biochemical level.

Drink Smarter with iBlush

iBlush was designed specifically for people with ALDH2 deficiency. Our Flush Patches, Flush Tablets, and Flush Gel work to support your body's ability to clear acetaldehyde — addressing the root cause rather than masking the visible reaction. Browse the full range at iblushshop.com.

P.S. We did the research so you don't have to: