If your body doesn’t take well to alcohol, you may be wondering why your BFF can down a bottle of vino on their own—whereas you’re left with flushing, fatigue, hives, or other side effects after barely polishing off one glass. Could it be that you’re intolerant to alcohol, or maybe allergic to it? And what’s the difference between an alcohol intolerance and an alcohol allergy, anyway?
Below, Gary C. Steven, MD, PhD, CPI, FAAAAI, FACAAI, FAPCR—founder of the Allergy, Asthma, and Sinus Center in Milwaukee and medical director of the American Academy of Allergy, Asthma & Immunology Registry—offers a sobering explanation on adverse reactions to alcohol.
Alcohol intolerance vs. alcohol allergy
To begin, alcohol intolerance is a genetic condition characterized by the inability to process alcohol efficiently. Dr. Steven explains that there are two enzymes involved in metabolizing ethanol, an intoxicating agent that exists in different amounts across wine, beer, and spirits.
“Alcohol dehydrogenase converts ethanol to acetaldehyde, which is toxic; and aldehyde dehydrogenase 2 (ALDH2) is an enzyme that converts acetaldehyde to vinegar, which is nontoxic,” Dr. Steven says. “People with a genetic deficiency in ALDH2 cannot clear acetaldehyde from the bloodstream,” indicating an intolerance or sensitivity to alcohol that can result in aldehyde poisoning. According to Dr. Steven, symptoms include the likes of “flushing, tachycardia, hypotension, headache, fatigue, nausea, vomiting, and diarrhea.” He adds that people of East Asian descent are more likely to be ALDH2 deficient.
Meanwhile, Dr. Steven mentions that alcohol allergy isn’t really a thing. Instead, another allergic reaction may be at play, which alcohol consumption may exacerbate rather than directly cause. “We cannot make antibodies to small molecules like ethanol,” he says. “We can, however, make IgE to proteins such as grains that may be present in fermented beverages. Distilled beverages are less likely to have proteins in them, but they may be introduced after distillation.” (For reference, the American Academy of Allergy, Asthma & Immunology notes that IgE are antibodies that the immune system produces in response to an allergen. These antibodies travel to cells that release chemicals, eliciting an allergic response.) Plus, as board-certified allergist Purvi Parikh, MD, previously told Well+Good, alcohol contains histamines, an excess of which “can worsen all underlying allergies by increasing inflammation in the body.”
In addition, Dr. Steven mentions that ethanol is a vasodilator—meaning it widens blood vessels, increases blood flow, and reduces blood pressure. As beneficial as these effects can be to promote circulation, the ethanol in alcohol can lead people with rosacea or other skin sensitivities to “manifest more significant symptoms from ethanol—such as flushing and itching—than others.”
How to deal with adverse reactions to alcohol
If you have true alcohol intolerance, Dr. Steven says that you don’t necessarily have to go cold turkey if you enjoy imbibing here and there. “People with alcohol intolerances can find a threshold through trial and error of how much ethanol they’ll tolerate before becoming symptomatic,” he shares. Sometimes, symptoms like flushing can be minor or even avoided with certain types of alcohol or intake levels, which—on the bright side—isn’t so awful compared to some of the more intense potential side effects of drinking with an ALDH2 deficiency. (For instance, as a half-Filipino, I discovered that I’m more prone to the “Asian glow” and headaches when I drink a glass of wine… though I can tolerate a few beers just fine. All in the name of research, of course.)
On the other hand, if you suffer from allergies that are heightened by alcohol intake, Dr. Steven says your best bet to start would be to address the root of the problem. For instance, if you have sensitive skin due to chronic hives and your symptoms come in full throttle when you drink, “treating the underlying condition that is leading to the overreaction will help you better tolerate ethanol,” he explains.
In the case of allergies (and, for that matter, overall health), it’s never a bad idea to limit your exposure to alcohol. “If someone has a genetic predisposition to develop allergic antibodies to certain proteins found in fermented beverages [like alcohol], they might develop an increasing reactivity to that beverage over time,” Dr. Steven shares. In other words, continued exposure can compound what was once a small reaction into something greater down the line. And while true alcohol allergies are rare, if your allergic response is severe when you drink, Dr. Steven advises doing away with alcohol altogether for safety’s sake. “Those who have a true allergic, and especially anaphylactic, reaction to a fermented beverage need to avoid it. There is no treatment that will predictably prevent anaphylaxis.”