Digestion changes might also play a role. There are cases where adults became allergic to a food they previously tolerated after taking antacids. This theory states that the lack of stomach acid reduces digestion and allows the protein to pass to the immune system intact. This probably does not account for many cases of allergy because antacids are widely used by those who never develop problems, but it raises a possibility that some change in digestion may be a factor.
Another possibility is that some insult against the immune system, for example a viral illness, might trigger an imbalance, leading to a new attack on an innocent food protein.
The problem in figuring out why a new allergy suddenly develops is that there are numerous possibilities and nothing has so far stood out as a clear reason. The long list of possibilities, well beyond the examples I have given, presents an active area for research.
It’s important to discuss your allergy with a board-certified allergist, and to consider any circumstances that might have differed at the time of the reaction, such as exercise, alcohol or medication use, which sometimes play a role in precipitating reactions. It is important to ensure you have the correct diagnosis, learn how to successfully avoid the trigger food(s), and know what to do in the event of a future allergic reaction.
Dr. Scott Sicherer is Chief of the Division of Allergy and Immunology of the Jaffe Food Allergy Institute at the Mount Sinai School of Medicine in New York. Together with Dr. Hemant Sharma, Associate Chief of the Division of Allergy and Immunology at Children’s National Medical Center in Washington, he writes “The Food Allergy Experts” column in the American Edition of Allergic Living magazine. Questions submitted below will be considered for answer in the magazine.