In contrast to flushing, irritant and toxic reactions to alcohol, allergic reactions to alcohol are relatively uncommon. In people with alcohol allergy, as little as 1 ml of pure alcohol (equivalent to 10ml of wine or a mouthful of beer) is enough to provoke severe rashes, difficulty breathing, stomach cramps or collapse. Alcohol can also increase the likelihood of severe allergic reactions (anaphylaxis) from other causes like food.
Allergy tests to alcohol are usually negative
The human body constantly produces small amounts of alcohol itself. Normal levels of 0.01 to 0.03 mg of alcohol/100 ml are contained in the blood. By contrast, a blood alcohol limit for driving of 0.05 per cent is equal to around 50 mg of alcohol/100 ml of blood. Since the human body produces alcohol itself, the reasons why some individuals develop allergic reactions when they drink alcohol is curious. Allergy tests using alcohol are usually negative, but are sometimes positive to breakdown products of ethanol such as acetaldehyde or acetic acid (vinegar).
Flushing is not an allergic reaction
Some people develop severe facial flushing if they drink small amounts of alcohol. This is not an allergic reaction and is most common in those with an Asian background. Other side effects may also occur, including fluttering of the heart (palpitations), feeling hot, headache, tummy discomfort or a drop in blood pressure These may be related to high blood acetaldehyde levels. Not all flushing is due to alcohol. Flushing can occur in skin conditions like rosacea, menopause, low blood sugar levels (hypoglycaemia), or as a response to some antibiotics or medicines used to treat diabetes or high blood fat levels.
Alcoholic beverages contain ethanol and other substances
The liver breaks down the alcohol (ethanol) that we drink and converts it to a chemical called acetaldehyde. Acetaldehyde is then transformed to acetic acid (vinegar). Problems occur if alcohol cannot be broken down. As well as ethanol, alcoholic beverages contain a complex mixture of grape, yeast, hop, barley or wheat derived substances, natural food chemicals (such as salicylates) and wood derived substances or preservatives like sodium metabisulfite. Severe allergic reactions have been described in people with allergies to proteins within grapes, yeast, hops, barley and wheat. These people are not sensitive to alcohol itself. Furthermore, fining agents (such as egg or seafood proteins) are sometimes used to remove fine particles. Whether these occur in sufficient amounts to trigger allergic reactions is unknown.
Asthmatic reactions may occur due to metabisulfite
Up to a third of people with asthma complain that wine will worsen their asthma, and ess often with beer or spirits. Beer, wine and champagne contain sodium metabisulfite (additive 220, 221) which have been used as a preservative since Roman times. Some people, particularly those with unstable or poorly controlled asthma, may wheeze when they consume these drinks. In general, there is more preservative in white wine than red wine, and more in cask wine than bottled wine. The amount of metabisulfite also varies from brand to brand. Some low sulfite wines are available, although those with extreme sensitivity may not be able to tolerate them. This is because some grape growers will dust sulfur powder over grapes in the weeks leading up to harvest. Other sources of metabisulfite include vinegar, pickled onions, dried fruit, crustaceans, some restaurant salads and fruit salads. Even when people complain that wine triggers asthma, metabisulfite may not be the only explanation. Information on Sulfite allergy is available on the ASCIA website: www.allergy.org.au/patients/product-allergy/sulfite-allergy
Asthma can also be due to enzyme deficiency
People with low levels of aldehyde dehydrogenase may accumulate high levels of acetaldehyde after drinking alcohol, as they cannot break it down easily. Acetaldehyde has been blamed for asthmatic reactions to alcohol in up to half of Japanese people with asthma.
Histamine and other substances may also cause problems
Histamine can trigger sneezing, runny nose and sometimes wheeze, stomach upset and headache. Although the actual amounts vary between different wines, in general there is more histamine in red than white wines and more in Shiraz than Cabernet. Some challenge studies suggest that antihistamines may reduce the severity of problems after wine, but as the challenges were equivalent to only one glass, these medicines probably won't prevent a hangover! Others substances in wine may also cause problems to some individuals, but these are not well defined.
The presence of alcohol may not always obvious
There are many less obvious sources of alcohol in our diet. These include alcoholic soft drinks, mixes, spiked drinks, food marinades or tomato puree. Over ripe fruit can ferment, resulting in enough alcohol production to trigger a reaction. Some medicines like cough syrups and some injected medicines also contain alcohol to help them dissolve and stay in liquid form.
Management of alcohol allergy
Accidental exposure to alcohol may lead to unexpected reactions. Severe alcohol allergy should be managed in the same way as other severe allergic reactions (anaphylaxis): identify and avoid the cause, wear a medical identification bracelet, and carry adrenaline (epinephrine) as part of an emergency action plan if individuals are at risk of potentially life threatening allergic reactions in the future. Information on anaphylaxis is available on the ASCIA website: www.allergy.org.au/patients/about-allergy/anaphylaxis
Milder reactions to alcohol may also occur
Alcohol sometimes worsens symptoms in people with hives (urticaria) and occasionally alcohol can trigger hives. As with more serious allergic reactions, the mechanism is unclear. Contact rashes from alcohol are very uncommon.
Not all adverse reactions to alcohol are due to allergy
Other effects of alcohol toxicity are well known, including its effect on the liver, stomach, brain and mental functioning when consumed in large amounts. Even though alcohol has a relaxant effect on the brain, some individuals will experience agitation and anxiety. and these symptoms are due to the drug like activity of alcohol. These reactions do not represent allergy anymore than a hangover does.
© ASCIA 2019
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Updated March 2019