For people who turn beet red when drinking alcohol, a casual hangout with friends at the bar can become a self-conscious ordeal. If you're one of these people, you're not alone. One in three people with East Asian descent (Chinese, Japanese and Korean) experience facial flushing when they drink, and it often only takes one drink to do it.
As a comprehensive breakdown of the problem in The Conversation points out, genetics are primarily to blame, although some environmental factors can play a role as well. Within Asian populations, though, it's mostly genetics. An inherited deficiency in the enzyme aldehyde dehydrogenase, which is involved in the breakdown of alcohol, is the culprit.
When you drink, your liver breaks down the alcohol into a particularly nefarious chemical called acetaldehyde. That's where your aldehyde dehydrogenase comes in, if you have it. This enzyme breaks down the acetaldehyde into harmless acetic acid (which is also a component of vinegar). If you can't convert the acetaldehyde fast enough — either because your body doesn't produce enough of it, or because you drink faster than your aldehyde dehydrogenase can handle — then you can become sick. In fact, this is the cause of many of those debilitating symptoms of hangovers.
And, it can make you flushed.
The bad news is, if you get flushed while drinking, you probably also begin to feel hungover more quickly. The good news is, this can be a boon to your health, because people who have such unpleasant experiences while drinking tend to drink far less, and thus have lower rates of alcoholism and alcohol-related cancers. In fact, there are drug treatments for alcoholism that work using this same principle, by blocking the activity of aldehyde dehydrogenase, thus making the experience of drinking alcohol unpleasant.
The other bad news, though, is that if you do have an aldehyde dehydrogenase deficiency and drink in spite of it, the condition can increase your health risks, especially regarding cancer.
So if you experience facial flushing when drinking, it's probably best to avoid alcohol as much as possible. If you do want to drink, however, you should probably only do so in extreme moderation. Listen to your body.