A. Food allergies are indeed related to your immune system—and, while it’s not exactly out of whack, it might be doing its job a little too zealously. Due to a genetic quirk, your immune system may recognize an otherwise harmless substance (such as milk) as a foreign invader and attack it, causing an allergic reaction.
In a true food allergy, your immune system mistakenly identifies a specific food or a component of food as a harmful substance and triggers certain cells to produce immunoglobulin E (IgE) antibodies to fight the allergen. The next time you eat even the smallest amount of that food, the IgE antibodies sense it and signal your immune system to release histamine and other chemicals into your bloodstream, which causes a range of allergic signs and symptoms, including dripping nose, itchy eyes, dry throat, rashes and hives, nausea, diarrhea, labored breathing and even anaphylactic shock. The majority of food allergies are triggered by certain proteins in eggs, peanuts, fish, shellfish (such as shrimp, lobster and crab), nuts (such as walnuts and pecans).
Other reactions to food don't involve your immune system or the release of histamine. These reactions aren't true food allergies but rather a food intolerance. The symptoms—nausea, vomiting, cramping and diarrhea—are often the same, although you may be able to eat small amounts of problem foods without a reaction.
See a doctor or allergist if you experience food allergy symptoms shortly after eating. Seek emergency treatment if you develop any signs or symptoms of anaphylaxis, such as constriction of airways that makes it difficult to breathe, rapid pulse, dizziness or lightheadedness. The only way to avoid an allergic reaction is to avoid the foods that cause signs and symptoms.