Blog
Alcohol intolerance
Covenant Metabolic Specialists Health Library
Covenant Metabolic Specialists
Physician Reviewed
Dec 3, 2025
Alcohol intolerance is a genetic or acquired condition in which your body has difficulty processing alcohol. Unlike a hangover, symptoms occur immediately or shortly after consuming even small amounts of alcohol. Common signs include facial flushing, nasal congestion, headaches, and nausea. Although often dismissed as “just getting red,” this reaction could point to underlying enzyme deficiencies, medication interactions, or other metabolic issues.
What is Alcohol Intolerance?
Alcohol intolerance is a condition where the body reacts negatively to alcohol—not due to overconsumption, but because it cannot metabolize alcohol properly. It’s most commonly caused by a deficiency in aldehyde dehydrogenase 2 (ALDH2), an enzyme responsible for breaking down acetaldehyde, a toxic byproduct of alcohol. When acetaldehyde builds up, symptoms appear quickly. Though not dangerous on its own, alcohol intolerance may indicate deeper metabolic or liver-related issues and may worsen with age or certain health conditions.
Symptoms
Symptoms typically begin within minutes of alcohol consumption and may vary in severity:
Facial flushing (especially cheeks and neck)
Stuffy or runny nose
Headache or migraine
Nausea or vomiting
Low blood pressure or rapid heartbeat (tachycardia)
Fatigue or lightheadedness
Hives or itchy skin
Diarrhea or upset stomach
Symptoms may resemble those of an alcohol allergy or other food sensitivities, but alcohol intolerance is rooted in metabolism—not immune response.
Causes
The underlying cause of alcohol intolerance depends on the type:
Genetic Alcohol Intolerance
Most commonly seen in people of East Asian descent (up to 40%)
Caused by an inherited ALDH2 gene mutation that reduces or blocks the enzyme’s function
Acquired Alcohol Intolerance
Medications (e.g., metronidazole, sulfonylureas, disulfiram)
Liver disease or fatty liver
Enzyme depletion due to chronic alcohol use or poor nutrition
Histamine sensitivity (red wine and beer contain high levels)
Sulfite sensitivity (preservatives found in some wines and spirits)
Risk Factors
You may be at higher risk for alcohol intolerance if you:
Are of East Asian descent
Have a family history of flushing or intolerance
Take medications that interfere with alcohol metabolism
Have chronic liver conditions (NAFLD, hepatitis, cirrhosis)
Suffer from asthma, mast cell activation syndrome (MCAS), or histamine intolerance
Use topical or oral antibiotics, antifungals, or diabetes medications
Diagnosis
There’s no single test for alcohol intolerance, but your provider can help pinpoint the cause through:
Medical history: Family symptoms, medication use, alcohol reactions
Symptom tracking: When and how symptoms occur after drinking
Allergy tests: To rule out true alcohol allergy (rare)
Blood tests: To evaluate liver enzymes or genetic testing for ALDH2 mutation
Challenge test: Controlled alcohol intake under supervision (rarely done)
Treatments
There’s no cure, but treatment focuses on avoidance and symptom management.
Avoid triggers:
Eliminate or reduce alcohol consumption
Identify specific beverages that worsen symptoms (e.g., red wine, beer)
Avoid alcohol when on interacting medications
Manage symptoms:
Antihistamines may help if histamine-related
Antacids for GI upset
Hydration and support for headaches and flushing
Enzyme supplements (not proven for ALDH2 deficiency, but some people try them)
Address underlying issues:
Manage liver conditions, histamine intolerance, or gut health. Switch medications if alcohol reactions develop suddenly
Prevention
Know your limits and observe your body’s response. Avoid alcohol if you’re on medications that list alcohol interaction as a side effect.
Stay away from high-histamine or high-sulfite drinks (aged wine, beer, champagne). Get screened for liver health or enzyme deficiencies if symptoms develop later in life.
Consider genetic testing if symptoms are severe or you have a family history.
Our Take
Most people shrug off alcohol flushing as embarrassing or annoying—but at Covenant, we see it as a metabolic clue. If your body reacts strongly to alcohol, especially with flushing, nausea, or racing heart, it may be more than just genetics.
It could point to liver dysfunction, histamine intolerance, or hormonal imbalances. We treat these as real symptoms—not something to power through. That glass of wine shouldn’t make you feel sick.
