It has been estimated that nearly two million Americans suffer from allergies to certain ingredients in alcoholic beverages. The consumption of alcohol typically brings a variety of reactions, including the dilation of the blood vessels, a reddening of the skin, and the swelling of the nasal passages. These reactions, however, are not the result of an allergy.Where such an allergy exists, it is usually one of the ingredients of alcohol such as yeast or sulphur dioxide (SO2) that triggers the reaction rather than the alcohol itself. Sulphites, eggs, grapes, corn, moulds and pesticides used to preserve or enhance the product can potentially become present in alcohol as part of the manufacturing process. The allergic reaction can include any or all of the indicators typically associated with allergies, including an itchy eye and nose, rhinitis, asthma, hives (urticaria), eczema, hives, or skin rashes, especially on the face or neck. Even if people are not allergic to alcohol itself, it can exacerbate the symptoms of existing allergies. Studies show that alcohol can interfere with the functioning of the immune system, potentially increasing an individual's sensitivities to other allergens.One of the main ingredients in wine is sulphur dioxide (SO2 or E220), also known as sulphites or metabisulphites. It is the key preservative in both red and white wine and prevents its oxidisation. Sulphur dioxide has antimicrobial properties that help it prevent the growth of spoilage yeasts, bacteria and micro-organisms in wine. Without the use of sulphites in wine there would be a greater possibility of the wine becoming contaminated by the materials used in the bottling process, including airborne moulds and bacteria on the glass or cork. This would create a commercially unacceptable degree of variation in the quality of the product.Sulphur dioxide is a naturally occurring compound that is typically found growing on plants. Because of its antibacterial qualities, the Romans used sulphites to prevent unwanted organisms from growing in the wine. By reducing the growth of yeast, the sulphites give the wine a longer shelf life and prevent it from turning into vinegar, allowing aged wine to develop more sophisticated flavourings.Sulphites are also used as preservatives in some fruit juices, dried fruits, fruit concentrates, canned fruit, jams, cheeses, and some processed vegetables. These items may trigger a reaction in an individual with an allergy to sulphites because they can potentially contain much higher levels of sulphites than wine does. A person with an allergy to sulphur dioxide should try to avoid consuming sulphites in the form of either food or drink.There are recognised limits to the amount of sulphur dioxide that winemakers can add to a wine. For example, the New Zealand Wine Institute has guidelines stipulating that any wine containing more than 25 parts per million (PPM) of sulphur dioxide is required to declare this on its label. Sulphur dioxide is added in small amounts (mg/L) at achieve the levels set by the regulatory bodies that are considered to be generally harmless to the majority of wine consumers. In the United States, the term "sulfites" on labels incorporates the total amount of free sulphur dioxide, hydrated sulphur dioxide, and other sulphites compounds such as metabisulphite in the wine. Other additives used in wines, including ascorbic acid and dimethylpolysiloxane, are also controlled by specific guidelines but without the legal requirement to list them on the label.Low levels of sulphur dioxide are usually produced naturally by yeast during the fermentation process and as by-product of the aging process. This means that sulphites are usually present in most wines even if the winemaker has not added them. A typical reaction to sulphites in alcohol may include dizziness, red flushes, wheezing or a shortness of breath. Headaches are more likely to occur as part of the reaction if the person is also an asthmatic.It has been estimated that approximately less than 1% of the population experience a negative reaction to sulphites so the condition is considered relatively rare. People who have an allergy to sulphites find that they experience effects out of all proportion with the amount of wine that they have consumed. A reaction to sulphites can make eyes difficult to focus and can cause a pounding headache after drinking as little as half a glass of wine.People with asthma should probably try to avoid those wines and beers with the highest concentration of sulphites. Wine is a frequent trigger for asthma, affecting about a third of asthmatics. Some asthmatics may experience asthma symptoms within a couple of hours of consuming a white wine containing sulphites. Others who suffer from asthma may experience coughing or a tightening of the chest after drinking wine as the sulphites in the wine induce spasms in the muscles of the lung's airways.A white wine will usually contain higher levels of sulphur dioxide than a red wine, and the sweeter the wine then the more sulphites it will contain. This is especially true of sweet white wines, with dry white wines containing less sulphur dioxide. Someone with a sulphur dioxide allergy will probably experience less of a reaction from a full-bodies red wine than from a white wine because the red has a lower sulphite content.Fining agents are another ingredient added during the wine making process. This "fining" process removes unwanted organisms, cloudiness, or fermentation in order to clarify the wine. During this process egg white, bentonite or some other fining agent is used to lift out the solids so that the clear wine can then be racked off. As no residue of these fining agents should remain in the finished wine there is usually no requirement for them to be declared on the label, although they are still regulated. If some trace of a fining agent is left, however, then it could possibly initiate an allergic reaction in someone susceptible to that particular allergen.While tannin may be present in small quantities in white wine, it is an essential characteristic of red wine. Tannin belongs to a group of chemicals known as polyphenols. It comes from the skin, pips and stems of the grapes. A wine may even incorporate oak tannin if it is aged in an oak barrel. Among the benefits that tannin provides are the structure that it gives the wine and the stabilisation of its red pigmentation through the aggregation of anthocyanins. It also has preservative qualities that allow the wine to age. As wine ages, the tannins gradually combine with the anthocyanins to soften the taste of the wine. Tannin, however, is believed to play a role in the incidence of "red wine headache".Although the exact cause of red wine headaches remains something of an enigma, it is postulated that it is at least partly caused by the vasoactive compounds contained in red wine. Red wine is also a well-known precipitant of migraines in people predisposed to migraines. The tannin in red wine may play a role in "red wine headache" as it prompts the release of the neurotransmitter serotonin, excessive amounts of which can cause migraines. One complication with this theory, however, is that people who do not suffer from migraines can get "red wine headache", while other products that contain tannin do not cause the same reaction. Others point to histamines or prostaglandins for a solution to this riddle but a conclusive answer has not been forthcoming. Of course, "red wine headache" should not be confused with the hangover that occurs hours after drinking.The most extreme reactions are usually caused by red wine, with dry white wines generally being milder, unless the individual is allergic to sulphur dioxide. White wines tend to have higher levels of sulphites by necessity because they are more at risk of oxidation than red wines. Another factor to consider is that the sulphites in white wines are not as easily absorbed as those in red. Unless you are allergic to sulphites, white wines are less likely to cause a reaction because they do not contain the skins of the grapes, the presence of which introduces other elements, including histamines. If you have an alcohol allergy then red wine may cause problems because it stimulates histamines. Those few people who react to high levels of histamine will exhibit symptoms resembling a food allergy The histamine in wine is bought out from the grape skin during the fermentation process. White wine, on the other hand, does not include the skin of the grape. To reduce the reaction caused by the histamine in wine, it is useful to remember that some types of fruit wine contain lower histamine levels than wines made from grapes. Histamine can also be found in other fermented products like aged cheese and chocolate.While an allergy to the yeast in wine and beer may not be common, it can result in an outbreak of hives. Technically there should only be a negligible amount of yeast in any finished wine because the yeast is only used as part of the fermentation process that turns grape juice into wine. A small amount of yeast breakdown product will remain after the process is completed and the wine is "racked off" and bottled.Different beers may contain wheat, rye, maize or corn as well as the usual ingredients of malted grain, water, hops and yeast. Unlike wine manufacturers, beer manufacturers have no legal requirement to list the ingredients used in their products, other than the food additives included. It is possible that sulphites or the residue of pesticide may still be present.Typically beer will only induce asthma in about one-third of asthmatics with a sensitivity to alcohol. While spirits like brandy, whiskey and vodka are not common triggers for asthmatics, alcoholic beverages like gin and whiskey may contain wheat. Wheat allergies can cause people to suffer from symptoms such as diarrhoea after drinking beer yet they might not react to other forms of alcohol not containing wheat.Generally speaking, drinking alcohol can lower the body's resistance to other allergies. Food eaten while you are drinking alcohol can pass into the bloodstream in a partially digested state only to be mistaken for an allergen because of its size, thereby prompting a reaction. Alcohol may also reduce the amount of the antioxidant glutathione present in the alveolar epithelial of the lung. The swelling alcohol stimulates in the nasal-sinus membranes can cause vasomotor rhinitis, a condition that will be complicated by any resident sinus infections.People who are sensitised to sulphur dioxide can try "No Preservative Added" (NPA) wines that have no sulphites added during the winemaking process. These organic wines and beers are designed to contain less sulphur dioxide, as well as avoiding synthetic fertilisers, hormones, toxic pesticides and chemical treatment agents during the manufacturing process. These products contain less antimicrobial agents, including amount half the level of sulphite used in other winemaking techniques. The level of sulphur dioxide in these wines due to yeast will vary between different strains of yeast and ferments, but will generally be less than 15 mg/litre.Other things you can try to lessen the effect of sulphites include drinking older wines that may have had their levels of sulphite reduced as they aged or you could perhaps try decanting a wine about an hour before you serve it to allow for some aeration.If you think that you have had an allergic reaction to a particular alcoholic beverage, you should take note of all the listed ingredients for the product and undergo a skin-prick test to see if you are allergic to that component of the drink. If nothing shows up in the test then you probably have an intolerance of one of the ingredients rather than an allergy. Food intolerance, also known as non-allergic hypersensitivity, does not generate a specific IgE response by the immune system. Instead, the reaction is dose dependent, with a clinical response only following once a dietary threshold is crossed. If you have intolerance to a substance then you should try to eliminate that ingredient from your diet. There is a non-allergic condition colloquially known as "Asian flush" that results from a low tolerance of the chemicals released when the body metabolises alcohol. Symptoms include a reddening of the face, neck, and ears, along with a feeling of sleepiness, possibly accompanied by a chill.