Your body will almost certainly rebel if you drink too much alcohol in a night. But what if it reacts after just a sip or two? If you notice odd symptoms like facial flushing, a runny nose, or even a racing heartbeat after drinking, you might not just be sensitive to alcohol—you could be allergic.
While true alcohol allergies are uncommon, they do exist, and alcohol intolerance and reactions to ingredients in your favorite drinks are pervasive. Here’s how to spot the clues that you might not get along well with alcohol.
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Is it an intolerance or an allergy?
Both involve different biological reactions, and an alcohol allergy can be dangerous.
A true alcohol allergy is an immune-system response to a component of the beverage. It may mean your immune system reacts to alcohol—or ingredients in alcoholic beverages like grains, yeast, or preservatives—as if it’s a harmful invader. Symptoms can include a rash; itching; swelling of the lips, tongue, or mouth; trouble breathing; stomach cramps; or even anaphylaxis, which can be potentially fatal.
An alcohol intolerance, on the other hand, “is a genetic or metabolic condition,” says Tamar Samuels, a registered dietitian and co-founder of Culina Health, a virtual nutrition platform. “People with an intolerance typically don’t have enough of the enzyme aldehyde dehydrogenase (ALDH2), which helps metabolize alcohol.” She says symptoms typically include flushing, nausea, rapid heartbeat, and headaches.
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Certain groups of people are prone to alcohol intolerance, though it can affect anyone. Up to 45% of East Asians carry the ALDH2 variant linked to alcohol flushing syndrome, which is a condition where your face, neck, or chest turns red soon after drinking alcohol. It’s usually caused by a genetic mutation that affects how your body breaks down alcohol.
Signs you might be allergic to alcohol
They’re rare, but alcohol allergies can range from mild to life-threatening, says Samuels.
Signs of an allergy emerge after drinking any amount of alcohol and can include skin reactions (like hives, itching, flushing, or eczema-like rashes), swelling of the face or throat (especially of the lips, eyes, or tongue), respiratory symptoms (like nasal congestion, sneezing, wheezing, or difficulty breathing), gastrointestinal symptoms (such as nausea, vomiting, stomach cramps, or diarrhea), or cardiovascular symptoms (like dizziness, fainting, or, in rare cases, anaphylaxis.)
How alcohol affects the body
Alcohol affects nearly every part of the body, starting with the brain. It slows down the central nervous system, impairing judgment, coordination, and reaction time. While it may create a temporary feeling of relaxation or euphoria, long-term use can lead to anxiety, depression, and addiction. Alcohol also alters how the brain’s reward system functions, which increases the risk of dependence over time.
“It also affects the heart in many ways, both directly and indirectly,” says Dr. Sean Heffron, cardiologist at the Center for the Prevention of Cardiovascular Disease at NYU Langone Heart.
It can impact blood pressure and influence levels of different types of cholesterol—specifically HDL cholesterol in the blood—and can also have an influence on heart rhythm and conduction. All of these impacts tend to be dose-responsive, meaning that depending on the amount of alcohol you drink, you can have variations in how each of these factors manifest.
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Alcohol has been classified as a known carcinogen and is linked to several cancers, including those of the breast, liver, mouth, throat, and colon. Even moderate drinking has been shown to raise the risk of breast cancer. It can also interfere with sleep, disrupt hormone levels, weaken the immune system, and contribute to weight gain and poor mental health.
“Because of these many negative side effects, drinking in moderation or not consuming alcohol all together is your healthiest option,” says Heffron.
Common allergic triggers in alcohol
Allergies to ethanol, the type of alcohol found in drinks, are exceedingly rare. Most reactions are caused by other compounds found in alcoholic beverages, says Heffron.
Histamines
Naturally occurring in fermented products like red wine and beer, histamines can trigger allergy-like symptoms in sensitive people, especially those with low levels of the enzyme diamine oxidase (DAO).
Sulfites
These preservatives, found in wine and beer, are especially problematic for people with asthma. One study suggests that sulfite sensitivity may affect up to 10% of people with asthma.
Grains
Beer and some spirits contain wheat, barley, or rye, which may trigger reactions in people with grain or gluten allergies.
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Flavorings and additives
Natural fruit compounds, artificial colorants, and tannins in wine can cause headaches, GI symptoms, or hives in sensitive people.
Ethanol or acetaldehyde sensitivity
In people with alcohol intolerance, the body lacks the enzyme ALDH2 needed to break down acetaldehyde, a toxic byproduct of alcohol metabolism. This causes flushing, nausea, and a rapid heartbeat.
What to do if you suspect you have an allergy
If you think you might have an allergy to alcohol, stop drinking immediately and take note of your symptoms.
“For mild symptoms (like hives or nasal congestion), an over-the-counter antihistamine may help,” says Samuels. “For more severe symptoms like trouble breathing, swelling of lips, or throat, seek emergency care immediately, as this could be anaphylaxis.”
She also recommends seeing an allergist for comprehensive testing, including patch testing or oral food challenges to identify the specific triggers like sulfites, grains, or histamines.
And is taking an antihistamine before you drink to prevent an allergic reaction a smart idea?
“It’s not recommended,” says Samuels. “While antihistamines may blunt some mild symptoms, they don’t address the root cause and can be risky when combined with alcohol.” That’s especially true for sedating antihistamines like diphenhydramine (Benadryl), which “can amplify alcohol’s effects, leading to increased drowsiness, impaired judgment, or even respiratory depression,” she says. “Instead of masking symptoms, it’s better to identify and avoid the trigger.”