Beer, one of the world's oldest beverages, is produced by a brewing process that uses yeast to ferment sugars from a starch, such as barley or wheat, to create alcohol. Although it's rare, some people do experience allergic reactions after drinking beer. According to research published in 2012 in the journal "Allergy," such a "beer allergy" is typically associated with particular proteins or ingredients that vary among beers and does not necessarily represent an allergy to all beer. Because many different proteins or ingredients can cause the allergic reaction, the symptoms and their severity vary from person to person. Any concerns about allergic symptoms after drinking beer should be discussed with your doctor.
Allergens From Barley
In 2001, research published in the "Journal of Allergy and Clinical Immunology" identified a common culprit in allergic reactions among people who drink beer: proteins derived from barley. The most common responses were hives and a more serious reaction called "angioedema" -- a skin rash like hives, with swelling that occurs beneath the skin, especially around the eyes or lips. If the swelling occurs in the mouth or throat, it may block the airway, causing wheezing or difficulty breathing or swallowing. Such symptoms would need immediate medical treatment.
Allergens From Sorghum
With many people choosing to go gluten free, more and more beers are now being brewed with sorghum instead of barley or wheat, which results in a gluten-free beer. Research published in 2014 in the "International Archives of Allergy and Immunology" described allergic reactions among 20 people after consuming beer. Hypersensitivity to sorghum was the most common reaction, found in 9 of those people, although researchers said those studied also showed reactions to other beer ingredients as well, including barley, hops and yeast. According to the researchers, the symptoms usually persisted for more than 2 hours and included hives, swelling, skin lesions and, in one case, fever.
It's even possible -- although apparently extremely rare -- for beer to cause an itchy skin rash or hives after coming into contact with skin. A case study published in 1995 in the journal "Contact Dermatitis" described a 20-year-old waitress who reported developing hives on her hands whenever she came into contact with beer at work. The waitress reported being able to drink beer without any allergic reaction. The authors speculated that the skin response was likely due to malt but brewer's yeast may also have contributed to the reaction.
Another case study, this one published in the journal "Allergy" in 2001, reported on a 21-year-old woman who experienced itchy skin and hives, swelling of the lips and face and wheezing and extreme difficulty breathing after drinking beer and eating a corn-based snack. Testing of the woman revealed she had multiple allergies, including allergies to barley, malt and corn. Such a reaction is typical of anaphylaxis, a severe, whole-body allergic response that results in a drop in blood pressure as well as narrowing of the airway so that breathing and swallowing become almost impossible. Case studies -- as opposed to research done with larger groups of people -- indicate that such a problem is extremely rare, and even this case study indicates that the woman had consumed other things she was allergic to -- not just beer. Nevertheless, if you experience them, severe symptoms such as these are life threatening and require immediate emergency medical treatment.