Primary cause of the hangover is a toxin Called acetaldehyde, which is produced in large quantities
by the liver when alcohol is ingested. Scientists consider acetaldehyde to be up to 30 times more
dangerous then alcohol itself, and builds rapidly during alcohol metabolism, causing symptoms such
as sweating, skin flushing, nausea, and vomiting, muscle aches, fatigue, headache or nausea, and
the notorious cognitive effects you experience during a hangover, like memory loss and irritation.

Acetaldehyde, a metabolite of ethanol (ie alcohol) is eventually excreted from the body as acetic acid.
We know that genetic factors play a role in the breakdown of alcohol, which is why hangover
symptoms vary from person to person.Some people, predominantly East Asians, have a mutation in
their alcohol dehydrogenase gene, which makes them convert ethanol to acetaldehyde unusually
fast. And, they break acetaldehyde down more slowly, leading to a very high concentration of
acetaldehyde. Some estimates say 6 as much as normal. And this leads to something known as the
alcohol flush reaction, where people’s neck and face turn quite red.

When consumed, ethanol circulates through the body and produces fun effects all over. Your brain
likes ethanol, that is why we (well most people anyway) drink. Your liver, as many of you know,
takes the biggest beating. When ethanol reaches the liver, it is immediately broken down.
Your liver is not capable of breaking down alcohol and its byproducts rapidly and essentially all of
the breakdown pathways become saturated at very low blood alcohol levels. Because of this backup
in the breakdown process, some byproducts hang around in the body for longer than we would like
and cause additional stress to the drinker.

Acetaldehyde deserves a large chunk of this blame. After ethanol reaches the liver, it is broken down
by alcohol dehydrogenase (ADH) into acetaldehyde. Acetaldehyde is then further metabolized by
aldehyde dehydrogenase (ALDH2) into acetate/acetic acid. Acetate is then circulated through the
body and excreted. The metabolism of alcohol to acetate causes the formation of reactive oxygen
species also known as free radicals.

These free radicals cause direct oxidative stress to tissue and organs throughout the body. Also, as
stated above, because humans can only process alcohol at a set speed and because the processing
pathways are quickly overrun, some of these metabolites hang around for longer than we would
like. Acetaldehyde becomes a particular issue in this case. Our body is naturally equipped with
measures to counteract free radicals. However, our body only have a limited supply of these antioxidants and once they are used up, free radicals generated by a buildup of acetaldehyde can cause
significantly more strain on the body.