Acetaldehyde can dilate capillaries. Once the facial capillaries dilate, some people will blush.

In other words, people who blush after drinking alcohol show that they can quickly convert ethanol into acetaldehyde, and such people have efficient alcohol dehydrogenase.

Extended data:

Alcohol dehydrogenase in the liver is responsible for oxidizing ethanol (a component of wine) into acetaldehyde, and the generated acetaldehyde is further converted into harmless acetic acid (a component of vinegar) under the catalysis of acetaldehyde dehydrogenase.

Acetaldehyde is more toxic than ethanol and is one of the main causes of hangover. Moreover, acetaldehyde is suspected of causing cancer, which has a certain relationship with the occurrence of human tumors.

Acetaldehyde dehydrogenase (ALDH) in liver is mainly responsible for the transformation of acetaldehyde in human body. It has two isoenzymes, which are distributed in cytosol (ALDH 1) and mitochondria (ALDH2) respectively.

References:

Acetaldehyde dehydrogenase-Baidu Encyclopedia