Causes

Most foods consumed need to be broken down and metabolised by enzymes once in our body. While some are digested in the stomach and small intestine before entering our blood system to be carried to their appropriate location, others are easily absorbed into the blood via the gastro intestinal track.

Alcohol is readily absorbed from the gastrointestinal tract, however, alcohol is a toxic compound and cannot be stored and therefore, the body must oxidize it to get rid of it.  Alcohol can only be oxidized in the liver, where enzymes are found to initiate the process. The enzyme Aldehyde Dehydrogenase (ALDH) metabolises alcohol into acetic acid (vinegar) a product from which the body can obtain some energy.

Some people have an alteration, called a polymorphism, in the ALDH gene which renders the enzyme inactive and makes it impossible for them to convert alcohol into acetic acid. Such persons should avoid alcohol, although they can enjoy the benefit of the antioxidants found in non-alcoholic red wine.

Symptoms

The consumption of alcohol can provide histamine and aids in the release of histamine. Alcohol prevents the breakdown of histamine. Moreover, histamine shares the same ALDH for its metabolism, hence an impaired ALDH enzyme will amplify the problem after the ingestion of alcohol which leads to excess histamine in the system. This leads to allergy-like symptoms including most notably nasal congestion and mild flushing of the skin within minutes of ingesting alcohol. Other side-effects include fluttering of the heart (palpitations, tachycardia), sensation of heat, headache, abdominal discomfort or a drop in blood pressure (hypotension) are related to high blood acetaldehyde levels.

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.
  
   

Other Conditions

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.. salicylates), 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.

Additives in wine, such as sulphites may cause allergy-like reactions in some.

Asthmatic Reactions:

Asthmatic reactions may occur due to sulphites (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 winemakers produce wines and state that they do not add sulphites into the wine. There are various technical reasons related to winemaking 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.