We've all met that person who goes bright red after a glass of wine or two.
It turns out there is a perfectly reasonable explanation - and it has nothing to do with people's tolerance to alcohol.
An article in Buzzfeed Science explains that "Alcohol Flush Syndrome", as the condition is called, is actually explained by a defective gene.
When you drink alcohol, there is an enzyme in your body that converts the alcohol into acetaldehyde, which is bad for you. Luckily, your body has another enzyme that counteracts that and quickly converts the acetaldehyde into acetate (which is pretty close to vinegar).
Some people have a deficient ALDH2 enzyme in their bodies and are not capable of metabolising alcohol properly.
This syndrome is strictly genetic and affects about half of the East Asia population, or descendants of Koreans, Japanese and Chinese. It can also affect some Southeast Asian people, such as Filipinos and Vietnamese.
Biochemist Kenneth Warren, Ph.D., deputy director of the National Institute on Alcohol Abuse and Alcoholism (NIAAA) in the US, told Buzzfeed Science that, while there is no cure, taking an antihistamine is thought to counterbalance the syndrome.