A food allergy occurs when your immune system responds defensively to a specific food protein that, in reality, is not harmful to the body.
The first time you eat the offending food, the immune system responds by creating specific disease-fighting antibodies (called immunoglobulin E or IgE). When you eat the food again, the IgE antibodies spring into action, releasing large amounts of histamine in an effort to expel the "foreign invader" from the body. Histamine is a powerful chemical that can affect the respiratory system, gastrointestinal tract, skin, or cardiovascular system.
What Are the Symptoms of a Food Allergy?
Symptoms of a food allergy may appear almost immediately, or up to two hours after you've eaten the food. Symptoms can include a tingling sensation of the mouth, swelling of the tongue and throat, hives, skin rashes, vomiting, abdominal cramps, difficulty breathing, diarrhea, a drop in blood pressure, or even a loss of consciousness. Severe reactions -- called anaphylaxis -- can result in death.
Which Foods Most Often Cause Allergic Reactions?
There are eight foods that cause over 90% of food allergies in children -- milk, eggs, peanuts, wheat, soy, and tree nuts (such as walnuts, pecans, and almonds).
In adults, 90% of food allergies are caused by peanuts, tree nuts, fish, and shellfish.
How Are Food Allergies Diagnosed?
Your doctor may do a radioallergosorbent blood test (RAST) to check the number of antibodies produced by your immune system. Elevated levels of certain types of antibodies can help your doctor identify specific food allergies.
By keeping a food diary, your doctor will have a much better starting point to determine the foods that could trigger your allergies. You may be asked to eliminate all potentially allergenic foods and then add them back to your diet one at a time to see if they prompt any reaction. This is called an elimination and challenge diet.
How Are Food Allergies Treated?
The best way to cope with a food allergy is to strictly avoid the foods that cause a reaction. Mild reactions often will subside without treatment. For rashes, antihistamines can help reduce itching and may also relieve congestion and other symptoms.
For more serious reactions, corticosteroids, such as prednisone, will help to reduce swelling. In life-threatening situations, an epinephrine injection can immediately begin to reverse symptoms and is the only effective treatment option. If a doctor has prescribed an auto-injector for you, carry two at all times.