Reactions to alcohol are frequent, have several different possible mechanisms and may involve different body organs.
The most frequent adverse reaction to alcohol is due to an enzyme deficiency (alcohol or aldehyde dehydrogenase), which is especially common in Asians, but the use of specific drugs (e.g. certain antibiotics) together with alcohol can cause or exacerbate the same symptoms.
Alcohol can also cause the release of histamine, with symptoms of histamine intolerance.
Alcoholic beverages contain many different components, which can potentially result in hypersensitivity reactions. Interestingly, these include barley, egg, grape, hop, seafood proteins, sulphites, wheat and yeast, wasp and bee remains (venom) which may cause severe reactions independent of alcohol itself. If these components are tolerated in other food, they are not the cause of the reaction to alcohol. These ingredients differ between and within types of alcoholic beverages.
Sulphites occur naturally in all wine, as well as in dried fruit, canned, bottled, or frozen fruit and juices, jams and jellies, vinegar, some salads, yogurt and other processed dairy goods, packaged pasta or rice mixes and may be used in the preparation of crustaceans. They are also routinely added as preservatives to beer, champagne and wine. They may precipitate asthma and wheezing in susceptible individuals, such as a proportion of asthmatics. The concentrations of sulphite increase from red wines to white wines to sweet wines, due to the amount of sulphites required to prevent spoiling. Organic wines may have less sulphites or have no additional sulphites added.
Overall, sulphites are unlikely to be responsible for many of the headaches and other symptoms besides respiratory effects seen during alcoholic beverage consumption.
Phenolic flavanoids (components in the skins of grapes related to tannins and responsible for conferring anti-oxidant benefits), or some of the amino acids in red wine may be the cause of many of the headaches reported. Red wine has a much higher content of both tannins and flavanoids than white wine. Tyramine and histamine are more plentiful in red than white wine and may cause symptoms in individuals intolerant to these biogenic amines.
Overindulgence in alcoholic beverages will lead to symptoms such as hang-over and withdrawal effects, or even chronic damage to body organs and should be avoided.
Frequency in population and natural history
Approximately 50% of Asians have the deficiency of alcohol or aldehyde dehydrogenases. The frequency of other alcohol reactions are not known, as they are poorly characterized.
The symptoms of a deficiency of alcohol or aldehyde dehydrogenases are typically flushing, irregular or increased heartbeat, headache, runny or stuffed nose, abdominal discomfort and blood pressure changes. Histamine release can cause similar symptoms, and generally also induces skin rashes and itch.
Headaches are caused by most of the above-listed alcohol reactions.
Testing and diagnosis
No specific tests are available for alcohol reactions, but genetic defects in alcohol or aldehyde dehydrogenases can be measured (polymorphisms) and are associated with higher esophageal cancer rates in heavy smokers and alcohol drinkers.
The general advice is to restrict the consumption of alcoholic beverages.