Wine is made from grapes and like grape, true allergic reactions are, thankfully, rare. If a grape allergy is suspected, it can be easily ruled out or confirmed with an allergy skin test.
Many people do however complain of problems when they drink wine and yet are not allergic to grape. If these reactions to wine are not an allergy to grape then what is causing the problem?
In most cases, ill effects reported after drinking wine are the result of a sensitivity to preservatives in the wine or to alcohol.
Sulfites are routinely added in the winemaking process as a preservative to prevent the growth of bacteria and unwanted yeast. Without sulfites, most wine will turn to vinegar. These sulfiting agents – sulfur dioxide, sodium potassium sulfite, bisulfite, and metabisulfite – can be added at different times and in varying amounts depending on the type of wine being made. In general, white wine has a higher sulfite content than red and sweeter wines have more sulfite than drier wines.
All wine contains naturally occurring sulfites so finding a wine that is completely sulfite-free would be unlikely. However, some winemakers offer organic wines with no added sulfites. In the US, new regulations in place since 2012 require that all wines with sulfite levels greater than 10 mg/L (ppm) be labeled as containing sulfites. Similar guidelines have been adopted by the EU and Britain.
Exposure to sulfites has been associated with a number of symptoms in sensitive individuals including anaphylaxis and hives. Although asthmatic symptoms are uncommon in patients with sulfite sensitivity without a history of asthma, serious and potentially life-threatening asthmatic reactions can occur in patients already under treatment for asthma.
In addition to wine, sulfites are added to a variety of foods including fruits, vegetables, and seafood to preserve freshness and prevent browning. Similar to wine, the FDA requires labeling on any food or beverage with greater than 10 mg/L (ppm) of these preservatives.
In addition to grape juice and preservatives, wine (of course) contains alcohol, specifically ethanol. As discussed in more detail in an earlier post (here), some individuals develop serious symptoms when they consume any form of alcohol. This is caused by a deficiency in a liver enzyme called aldehyde dehydrogenase. Without this enzyme, high levels of the chemical acetaldehyde accumulate in the blood. Acetaldehyde can cause symptoms that resemble an allergic reaction including facial flushing, nasal congestion, respiratory difficulty, nausea, and headaches when they drink any form of alcohol.
Some reports suggest that wine may contain varying amounts of acetaldehyde in addition to ethanol. This may explain why some people are able to tolerate certain varieties of wine but not others.
What About Yeast?
Yeast is the engine that turns common grape juice into highly valued wine. The industrious yeast eat the sugar in the grapes and as a waste product produces ethanol. Although wild yeast found natively on the surface of harvested grapes has been used in winemaking for centuries, most winemakers today add yeast to ensure consistent results. Saccharomyces cerevisiae is the variety of yeast most frequently used in winemaking. It is also the yeast used in beer making and baking and is commonly called brewer’s yeast.
Although brewer’s yeast is an allergen, there are few reports of allergy to the yeast causing problems drinking wine or beer or eating bread. It is, however, a significant cause of occupational allergy for those exposed to high levels of airborne yeast in the workplace such as a baker. As an interesting side note, this yeast also grows on our skin and can be a cause of yeast infections in women.
Why is brewer’s yeast a problem in the air and not in wine? Although wine production starts with living, growing, feasting yeast cells, rising levels of alcohol in the wine will eventually kill a large percentage of the yeast and are removed from the final product when they precipitate out.
How Do I Know What is Causing My Problems When I Drink Wine?
As mentioned above, allergy to grape can be determined with an allergy skin test. Allergy testing is also available for sensitivity to Saccharomyces cerevisiae yeast, although a positive test result does not necessarily mean that yeast in the wine is causing problems. Diagnosing alcohol and sulfite sensitivity is more challenging and requires a careful history by a physician experienced with these syndromes and a controlled food challenge.