Alcohol sensitivity: why alcohol makes you feel sick
Many people can enjoy a drink without trouble, but for some, even a single glass of wine triggers uncomfortable symptoms - flushing, nausea, headaches, or a rapid heartbeat. This reaction might not be a typical hangover. Instead, it could be a sign of alcohol sensitivity, a genetic condition that prevents the body from processing alcohol efficiently. Even small amounts of alcohol can cause discomfort if you're sensitive to it, and many people don’t realise their symptoms aren’t just from a typical hangover. Recognising the signs of alcohol sensitivity early - such as facial flushing or nausea shortly after drinking - can help you make informed choices and avoid unnecessary discomfort.
What is alcohol sensitivity?
Alcohol sensitivity (also called alcohol intolerance) is a genetic condition where the body lacks the proper enzymes to break down alcohol. Specifically, individuals may have a variant in the ALDH2 gene, which reduces the body’s ability to metabolise acetaldehyde, a toxic byproduct of alcohol metabolism. This results in acetaldehyde buildup, causing symptoms such as facial flushing, nausea, headaches, and low blood pressure.
Unlike alcohol allergy (which involves an immune response to alcohol or its ingredients), alcohol sensitivity is purely metabolic. It often runs in families and is more common in individuals of East Asian descent, although it can affect anyone.
Symptoms associated with alcohol sensitivity
People with alcohol sensitivity often experience rapid and visible symptoms, including:
- Red, flushed skin (especially on the face and chest)
- Headaches or migraines shortly after drinking
- Nausea or vomiting
- Rapid heartbeat or palpitations
- Nasal congestion or runny nose
- Low blood pressure and dizziness
These reactions can occur with even small amounts of alcohol, making even occasional drinking potentially uncomfortable. When drinking socially, symptoms might be dismissed as overindulgence or stress - but they could be signs of your body rejecting alcohol at a chemical level.
Why alcohol sensitivity can flare up
Several factors can combine to intensify symptoms for people with alcohol sensitivity:
- High alcohol consumption: Events like birthdays, weddings, office parties or weekend gatherings can lead to drinking more frequently or in larger amounts.
- Richer meals: Foods high in histamines (e.g. cheese, cured meats) can exacerbate reactions.
- Increased stress: Emotional stress can heighten histamine responses and reduce alcohol tolerance.
- Fatigue and dehydration: Lack of sleep and low hydration levels worsen symptoms like headaches or nausea.
You may feel particularly unwell after drinking not just due to alcohol itself, but because your tolerance is already under strain.
The genetic link in alcohol sensitivity
The main cause of alcohol sensitivity is a genetic mutation that affects the body’s ability to break down alcohol. The most common is a variation in the ALDH2 gene, leading to a deficiency in the enzyme aldehyde dehydrogenase. This causes a buildup of acetaldehyde, which has been reported to be 10 to 30 times more toxic than alcohol itself.
Other gene variants, such as those in ADH1B, can also affect how quickly alcohol is converted to acetaldehyde - meaning some people produce it faster than their body can clear it.
Genetic predisposition means some people are simply more prone to discomfort when drinking. If symptoms have persisted for years or seem to worsen over time, genetic factors are likely playing a role.
The role of at-home testing
Understanding your genetic predisposition to alcohol sensitivity can be an empowering step towards managing how alcohol affects your health and wellbeing. MyHealthChecked's Intolerances & Sensitivities DNA Test is designed to uncover whether you carry genetic markers associated with common food and drink sensitivities - including a predisposition to alcohol intolerance. By analysing variants in key genes such as ALDH2 and ADH1B, this test can help explain why you might experience unpleasant side effects from drinking alcohol, such as flushing, headaches or nausea.
The process is simple and fully at-home: collect your sample using a cheek swab and send it to our laboratory for analysis. Your results are typically ready within 28 days and come with personalised nutrition guidance developed by healthcare professionals. In total, the test screens 13 genetic markers across six health areas, providing you with a broader view of your dietary sensitivities. It provides meaningful insight into the potential genetic drivers behind your symptoms, helping you make more informed and personalised lifestyle and nutrition decisions.
How to manage alcohol sensitivity
You don’t have to give up alcohol entirely, but being prepared can help you avoid unpleasant symptoms. Here’s how to reduce the impact of alcohol sensitivity:
- Stay hydrated: Drink water before, during and after alcohol to avoid dehydration.
- Eat beforehand: Having a meal (especially one rich in protein and healthy fats) slows alcohol absorption.
- Choose drinks wisely: Clear spirits like vodka or gin tend to cause fewer reactions than red wine or beer.
- Limit histamine-heavy foods: Aged cheeses, cured meats, and fermented foods can heighten symptoms.
- Skip the top-up: Know your limit and avoid pressure to keep drinking.
- Take breaks: Alternate alcoholic drinks with non-alcoholic ones like sparkling water or herbal tea.
Listen to your body. If you feel flushed, dizzy, or nauseous early on, that’s a sign to stop drinking.
Frequently asked questions
1. Can alcohol cause skin rashes or flushing?
Yes. Facial flushing and rashes are common signs of alcohol sensitivity, often caused by acetaldehyde buildup due to a genetic enzyme deficiency.
2. Why do I feel sick after one drink?
If you experience nausea, headache or a rapid heartbeat after just one drink, it may be due to alcohol intolerance. This isn’t a hangover - it’s a metabolic reaction.
3. Are certain drinks better for alcohol intolerance?
Yes. Clear spirits like vodka or gin usually cause fewer symptoms than wine or beer, which are higher in histamines and congeners.
4. How do I know if I have alcohol sensitivity?
A DNA test like MyHealthChecked’s Intolerances & Sensitivities DNA Test can identify genetic markers related to alcohol intolerance.
5. Does alcohol sensitivity get worse with age?
It can feel worse over time, especially if other factors like stress or health changes are involved. Genetic alcohol sensitivity itself doesn’t change, but tolerance may decline with age or lifestyle shifts.
In summary
Alcohol sensitivity is a genetic condition that can cause symptoms such as flushing, nausea, headaches, and a rapid heartbeat. These reactions often appear quickly and may be mistaken for the effects of overindulgence, especially when stress, rich food, and frequent alcohol consumption collide. Understanding your body's response to alcohol and recognising the signs of intolerance early can help you make more informed decisions and avoid unnecessary discomfort. An at-home DNA test, like our Intolerances & Sensitivities DNA Test, offers personalised insights into whether your symptoms are rooted in your genes. The key to feeling your best is recognising your limits, drinking mindfully, and making informed choices based on how your body responds.
References
1. Mayo Clinic. Alcohol intolerance - Symptoms & causes. 2025 https://www.mayoclinic.org/diseases-conditions/alcohol-intolerance/symptoms-causes/syc-20369211
2. Alcohol Change UK. Why does my face go red when I’m drinking? Understanding alcohol intolerance. 2025. https://alcoholchange.org.uk/alcohol-facts/fact-sheets/why-does-my-face-go-red-when-im-drinking-understanding-alcohol-intolerance
3. Allergy UK. Reactions to alcohol. 2022. https://www.allergyuk.org/resources/reactions-to-alcohol/
4. BBC Good Food. Best foods to eat before drinking. 2025. https://www.bbcgoodfood.com/health/best-foods-to-eat-before-drinking
5. Guo R, Ren J. Alcohol and acetaldehyde in public health: from marvel to menace. Int J Environ Res Public Health. 2010;7(4):1285-1301. doi:10.3390/ijerph7041285. https://www.mdpi.com/1660-4601/7/4/1285