A food allergy is an adverse immune response to certain kinds of food. The protein in the food is the most common allergic component.
Food allergies occur when the body's immune system mistakenly identifies a protein (allergen) as harmful and stimulates lymphocytes to produce the IgE antibody that is specific for the allergen. This IgE then is released and attaches to the surface of the mast cells in various tissues and basophils in the blood in a process known as sensitization. No symptoms occur during the sensitization phase but, once that phase is completed, the individual is primed to react to the offending allergen.
The next time the person eats that particular food, its allergen hones in on the specific IgE antibody on the surface of the mast cells and prompts the cells to release chemicals such as histamine. Depending upon the tissue in which they are released, these chemicals cause the various symptoms of food allergy.
Symptoms of food allergy include:
- Itching or swelling in the mouth
- Vomiting, diarrhea, or abdominal cramps and pain
- Hives or eczema
- Tightening of the throat and trouble breathing
- Drop in blood pressure
The foods that most often trigger allergic reactions include cow’s milk, eggs, fish, peanuts, shellfish, soy, tree nuts and wheat.
Many food allergies are first diagnosed in young children, though they may also appear in older children and adults. Allergic reactions can range from mild to severe and are associated with the rapid onset of symptoms – usually within a few minutes.
Food allergy reactions can be life-threatening, so people with this type of allergy must be very careful to avoid their food triggers. People diagnosed with a food allergy may carry an auto-injector device containing epinephrine (adrenaline).
Epinephrine is the first-line treatment for severe or life-threatening allergic reactions (anaphylaxis). Epinephrine can reverse severe symptoms. However, it must be administered promptly during anaphylaxis to be most effective. Continued patient education on the importance of having an epinephrine autoinjector easily accessible, especially when eating, is important.