If you flush when you drink, this is why — and it matters for hangovers too
Some people turn red after a glass of wine. Others can drink the same amount and barely notice a thing. That difference isn't tolerance or willpower — it's genetics, and it comes down to a single enzyme: ALDH2.
We covered what ADH and ALDH actually do in a separate piece. This one is about a specific, common variant of ALDH2 that changes how that whole process plays out — legitimate, well-documented human genetics, not a wellness-influencer talking point.
What ALDH2 deficiency actually is
ALDH2 is the enzyme responsible for clearing acetaldehyde, the toxic byproduct of alcohol metabolism. A common genetic variant — ALDH2*2 — produces a version of the enzyme that works far less efficiently. It's most prevalent in people of East Asian descent, affecting an estimated 30–50% of that population, which is why the flushing reaction is often called "Asian flush" or "alcohol flush reaction."
People with one copy of the variant (ALDH2*1/*2) clear acetaldehyde more slowly than people with no copies. People with two copies (ALDH2*2/*2) clear it slower still, and often avoid alcohol almost entirely because the reaction is so pronounced.
What this means for hangovers specifically
The 2013 Korean pear study we cover in the study behind the pear tested for exactly this. The results were nuanced, and we think the nuance is worth stating plainly rather than smoothing over:
- Pear juice lowered blood alcohol levels for everyone in the study, regardless of ALDH2 genotype.
- But improvements in specific symptoms — memory, light and sound sensitivity — were significant for participants with ALDH2*1/*1 or ALDH2*1/*2 genotypes, and not significant for those with ALDH2*2/*2.
In plain terms: the metabolic benefit is broad, but symptom relief may vary depending on your own genetics. We'd rather tell you that than let a headline number do more work than it should.
Why we're telling you this instead of hiding it
Understanding your own biology isn't a downside to drinking — it's part of doing it on your own terms. If you already know you flush or get hit harder than your friends, that's not a personal failing, it's ALDH2. Planning around it is a more useful response than guessing.
Source: Lee, H.S., Isse, T., Kawamoto, T., Baik, H.W., Park, J.Y., & Yang, M. (2013). Effect of Korean pear (Pyrus pyrifolia cv. Shingo) juice on hangover severity following alcohol consumption. Food and Chemical Toxicology.