Can you be allergic to alcohol?
The short answer is, “Yes”. The full picture is a bit more complicated.
To start we need to distinguish true allergic reactions to alcohol from what we might broadly call “adverse reactions”. In an adverse reaction, bad things happen when you consume an alcoholic drink but the mechanism for the reaction may or may not be allergy.
When we discuss the “alcohol” in the alcoholic beverages we drink we are referring to the chemical ethanol. There are other alcohols such as methanol (wood alcohol) that have a variety of applications, but most are too toxic to drink. That brings up an important point.
Alcohol is a Poison
Ethanol is a toxin. It’s primary toxic effect is to temporarily depress our central nervous system. This is where we get the term “intoxicated”. Very high doses can cause respiratory depression, coma, and death.
Ethanol is detoxified or metabolized in the liver. If we do not detoxify the ethanol we drink, levels in the body will continue to increase until we lose consciousness. This detoxifying process depends on an enzyme in our liver called alcohol dehydrogenase and produces the chemical acetaldehyde. Acetaldehyde is metabolized further by the enzyme aldehyde dehydrogenase. We consume ethanol. The ethanol is converted to acetaldehyde in the liver and the acetaldehyde is detoxified further by the enzyme aldehyde dehydrogenase. This last part is important because without the enzyme aldehyde dehydrogenase, the body cannot get rid of the acetaldehyde and it will accumulate in the body. Acetaldehyde is not as toxic to the brain as ethanol, but high levels can cause facial flushing, nausea, headaches, and rapid heart rate.
An estimated 30-50% of East Asians (Chinese, Japanese, and Koreans) do not make sufficient amounts of the enzyme aldehyde dehydrogenase and will get sick when they drink alcohol.
This reaction to alcohol has been called the alcohol flush reaction. In addition to flushing, drinking alcohol can cause nasal stuffiness and asthma-like respiratory symptoms in individuals who have a deficiency in aldehyde dehydrogenase.
Redness of the skin, nausea, nasal congestion and difficulty breathing – all this sounds like a typical allergic reaction. It is not a true allergic reaction however because the mechanism is the accumulation of a toxin in the body of susceptible individuals because of an enzyme deficiency and not because of an immunologic allergic sensitivity.
People with a sensitivity to aspirin (aspirin-induced respiratory disease) may also experience an increase in respiratory symptoms after drinking alcohol, even if they have not taken aspirin.
In addition to ethanol, some alcoholic drinks, particularly wine, may contain high levels of other chemicals such as sulfites and even acetaldehyde. (reviewed here)
All of these very unpleasant symptoms caused by drinking alcoholic beverages are either the direct effect of ethanol, metabolites or other chemicals present in the drink. I review more about allergic reactions to beer, here, and to wine, here.