An adverse reaction to the ingestion of alcohol caused by a deficiency of the enzyme that is needed to breakdown alcohol. Alcohol unless broken down is toxic to our body and an immediate immune response is triggered causing symptoms typical to an allergy.
When we consume food, with the exception of a few, is first broken down by enzymes produced by our body to become fully absorbed. Otherwise, our body may react. Alcohol, once consumed is able to enter our blood straight away, however, an enzyme produced by the liver, called Aldehyde Dehydrogenase (ALDH) breaks it down into vinegar (acetic acid). Some people do not produce enough ALDH or do not produce enough. Hence the alcohol remains in the system and is nothing but a toxin that will trigger the immune system and causes allergic-like reactions. Such persons should avoid alcohol.
Some people are born with a slightly altered ALDH (defective in other words), which renders the enzyme ineffective, leaving the alcohol in its original state causing allergic-like reactions as well.
The commonest abnormal reaction to alcohol is seen in persons from an oriental background, who get flushing, increased heart rate, and symptoms of reduced blood pressure. This is sometimes referred to as 'oriental flushing syndrome'. Approximately 50% of Chinese, Japanese, and Koreans are deficient in ALDH, and this has been reported to be protective against the development of alcoholism.
Other causes and symptoms:
- Certain drugs like Metronidazole (antibiotic) and Griseofulvin (antifungal) can inhibit the effect of ALDH and cause the oriental flushing syndrome.
- The vasodilatory effect of alcohol in the stomach can increase the absorption of food allergens in the stomach and could aggravate food allergies.
- Alcohol causes the release of histamine and some wines have a high concentration of histamines.
- Alcohol is a very common trigger for vasomotor rhinitis.
Alcoholic beverages are complex. As well as ethanol, alcoholic beverages contain a complex mixture of grape, yeast, hop, barley or wheat-derived substances, natural food chemicals (e.g. salicylate), wood-derived substances or preservatives like sodium metabisulphite. Furthermore, "fining agents" may be used to remove particulate matter. These include the use of egg protein in some wines or seafood proteins to fine some beers.
Asthmatic reactions may occur due to sulphites. Up to a third of patients with asthma complain that wine will worsen their asthma, less frequently with beer or spirits. When patients wheeze after drinking alcohol, there are a number of possible reasons. Beer, wine and champagne contain sodium metabisulphite (additive 220, 221), used as a preservative since Roman times. Some patients, 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 metabisulphite also varies from brand to brand. Some "low sulphite" wines are available, although those with extreme sensitivity may not be able to tolerate them, as sulphur powder is sometimes dusted over grapes in the weeks leading up to harvest . Other sources of metabisulphite include vinegar, pickled onions, dried fruit, or when dusted onto crustaceans and some restaurant salads or fruit salads. Even when people complain that wine triggers asthma, metabisulphite is not always the trigger.
Sulphite in Wines
As a rule, sulphites are found at higher levels in the cask wine than bottled wine, and are at much higher concentrations in white wine than red wine, when natural tannins help preserve the beverage. Some wine makers produce wines and state that they do not add sulphites into the wine. There are various technical reasons related to wine making why very low levels of sulphites might still be present, even when not added to the wine itself.
Others substances within wine may also cause problems to some unlucky individuals, but these are not well defined. Serious allergic reactions to beer or wine may occur Anaphylaxis has been described in patients with severe allergic reactions to proteins within grapes, yeast, hops, barley and wheat. These patients are not sensitive to alcohol itself.
Alcohol & Allergy
Allergic reactions to alcohol itself are rare, but described in a few dozen published case reports. 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, a condition known as anaphylaxis. Given that the body constantly produces small amounts of alcohol itself, the reason that such reactions occur is poorly understood.
Mechanisms of Alcohol Allergy
The mechanism of allergic reactions to alcohol is uncertain. It is not thought to be IgE mediated, and it is likely that the breakdown products of alcohol such as acetic acid or acetaldehyde are unlikely to trigger allergic reactions either. Hypotheses include contaminants with alcohol, happen carrier responses, alcohol or metabolite conjugates.
Alcohol Allergy Testing
In published case reports, all patients thus far have had negative skin test to ethanol. Some have had positive skin prick testing to acetic acid or acetaldehyde but not always, and some have had allergic reactions on challenge to alcohol, acetic acid or both. Some patients who have had positive reactions to acetic acid on skin testing, yet have had negative challenges. Finally, alcohol can sometimes act as a "co-factor", increasing the likelihood of anaphylaxis from other causes.