Food allergies are your body's way of saying it's confused. Although most foods are perfectly safe to eat, your immune system mistakenly identifies the proteins in specific foods as harmful and overreacts when you eat them. It releases antibodies called immunoglobulin E, or IgE. Then each time you come in contact with that food allergen in the future, your body will again release antibodies. Once antibodies are released, a team effort is launched in your body in order to neutralize the "invading" allergen. One member of the team, histamine, is responsible for most of your allergic symptoms.
While the most common allergic symptoms associated with food allergies involve sneezing, nausea, hives, swelling and the like, food allergies can also cause anaphylaxis on rare occasions. The food allergies most likely to cause anaphylactic shock are allergies to peanuts, tree nuts, dairy, eggs, shellfish and fish. Anaphylaxis is a potentially life-threatening condition in which your respiratory system, gastrointestinal system, circulatory system and your skin go haywire. It can set in a few minutes to a half-hour after you eat a food you're allergic to. You can end up itching, swelling, coughing and vomiting. In addition, your airways will constrict and you'll feel like there's a lump in your throat that makes it hard to breathe. Your blood pressure will drop and your pulse will speed up. You might even pass out. Anaphylaxis requires immediate medical attention; otherwise, it can be fatal.
Once you discover that you're at risk for anaphylaxis, you have to be extra careful to avoid the foods that might trigger it. In addition, your doctor will probably want you to carry an autoinjector of epinephrine with you at all times. That way, if you do end up going into anaphylaxis, you're ready.