Like any food or beverage, coffee can trigger an allergic reaction in those who are sensitive to it. That said, the caffeine in coffee can also create a number of side effects that are unrelated to allergies, including upset stomach, jitteriness and irregular heartbeat. If you experience any unusual symptoms after drinking coffee, see your doctor for a diagnosis.
Coffee and Allergies
If you are allergic to coffee, you're likely reacting to the caffeine. However, there's a small chance that you may be sensitive to other substances. In 2012, Baylor University Medical Center reported what it referred to as the first known adult case of angiodema -- allergy-induced swelling -- from instant coffee that was not related to caffeine. Other signs of an allergic reaction include nausea, vomiting, abdominal pain and diarrhea.