Food Allergies

A food allergy occurs when your immune system responds defensively to a specific food protein that is not harmful to the body.

The first time you eat the offending food, your 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 your 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 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?

The following foods cause over 90% of food allergies - milk, eggs, fish, shellfish, peanuts, wheat, soy, and tree nuts (such as walnuts, pecans and almonds).

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.

The doctor may also perform an allergy skin test, also called a scratch test, to identify the substances that are causing your allergy symptoms.

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, skin creams may ease discomfort while antihistamines can help reduce itching 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.

How Can I Be Prepared?

Once you and your doctor have determined which foods you should avoid, stay away from them. However, it is important that you maintain a healthy, nutritious diet. Ask your doctor to recommend foods that will provide you with the necessary nutrients.

You should also be aware of the ingredients in processed foods. Be sure to read labels. A registered dietitian can help you learn how to read food labels to discover hidden sources of food allergens.

If you are prone to allergic reactions, ask your doctor to prescribe an epinephrine injection kit and carry it with you at all times.