Food allergies occur when your body comes in contact with a certain food, whether by digestion or simply breathing in the air around the food, that your body thinks is trying to harm you. When you have a food allergy, a specific food will trigger your immune system into thinking that part of the food is harmful. Your body will then tell cells to release an antibody called immunoglobulin which will neutralize the allergen.
For some, allergic reactions may be as simple and non-threatening such as an upset stomach, while some may have a more severe and life-threatening reaction such as anaphylaxis shock which includes extreme swelling of the airways, making it impossible to breathe.