Asian glow, or alcohol flush syndrome, is not the inability to metabolize alcohol. Instead, 80% of Asians have gene variants of alcohol dehydrogenase that metabolize ethanol to acetaldehyde more efficiently.

In addition, around 50% of Asians also express the mitochondrial ALDH2 allele, exclusively inherited maternally, which inhibits the acetaldehyde dehydrogenase enzyme. What ensues is the buildup of acetaldehyde, causing red flushes or botches known as Asian Glow.

Crystallographic structure of alcohol dehydrogenase

Strangely, people with the mitochondrial ALDH2 allele often turn red  and exhibit the physical appearance of drinking more while metabolizing alcohol more quickly. The result is they do not feel “buzzed” or drunk yet appear to be so.

Crystallographic structure of acetaldehyde dehydrogenase

The International HapMap Project, a human genome project to uncover genetic patterns, observed that the rs671 allele of the ALDH2 gene responsible for Asian Glow is native to East Asia. The allele is postulated to have originated in Han China and positively selected for at some point. Elevated acetaldehyde may confer protection against some parasitic infections.

Heartburn medicine, alka-seltzers, and H2-antagonists are often anecdotally touted for effectiveness in preventing or counteracting Asian Glow, but claims are not substantiated by randomized, controlled studies.

There is evidence from animal studies that glucose and fructose, monomer carbohydrates, increase ethanol metabolism in an alcohol-dehydrogenase-independent pathway.

Some drinkers also claim tolerance for ethanol can be built up through regular training, but since acetaldehyde is carcinogenic (cancer-causing), excess drinking should probably be discouraged.

Source 1, 2, 3