How we diagnose an allergy

For some people, an allergic reaction to a particular food may be uncomfortable but not severe. For other people, an allergic food reaction can be frightening and even life-threatening. Food allergy symptoms usually develop within a few minutes to two hours after eating the offending food. Food allergies can occur even the first time you eat a food.

The most common food allergy symptoms include:

*Tingling or itching in the mouth
*Hives, itching or eczema
*Swelling of the lips, face, tongue and throat, or other parts of the body
*Wheezing, nasal congestion or trouble breathing
*Abdominal pain, diarrhea, nausea or vomiting
*Dizziness, lightheadedness or fainting

Anaphylaxis

In some people, a food allergy can trigger a severe allergic reaction called anaphylaxis. This can cause life-threatening symptoms, including:

Constriction and tightening of airways
A swollen throat or the sensation of a lump in your throat that makes it difficult to breathe
Shock, with a severe drop in blood pressure
Rapid pulse
Dizziness, lightheadedness or loss of consciousness
Emergency treatment is critical for anaphylaxis. Untreated, anaphylaxis can cause a coma or death.

Exercise-induced food allergy

Some people have an allergic reaction to a food triggered by exercise. Eating certain foods may cause you to feel itchy and lightheaded soon after you start exercising. In serious cases, an exercise-induced food allergy can cause reactions such as hives or anaphylaxis. Not eating for a couple of hours before exercising and avoiding certain foods may help prevent this problem.

Pollen-food allergy syndrome (Oral Allergy Syndrome)

In many people who have hay fever, fresh fruits and vegetables and certain nuts and spices can trigger an allergic reaction that causes the mouth to tingle or itch. In some people, pollen-food allergy syndrome — sometimes called oral allergy syndrome — can cause swelling of the throat or even anaphylaxis. This is an example of cross-reactivity. Proteins in fruits and vegetables cause the reaction because they're similar to those allergy-causing proteins found in certain pollens. For example, if you're allergic to ragweed, you may also react to melons; if you're allergic to birch pollen, you may also react to apples. Cooking fruits and vegetables can help you avoid this reaction. Most cooked fruits and vegetables generally don't cause cross-reactive oral allergy symptoms.

PICTURE OF ORAL ALLERGY SYNDROME CHART GOES HERE

When to see a doctor

See a doctor or allergist if you have food allergy symptoms shortly after eating. If possible, see your doctor when the allergic reaction is occurring. This will help your doctor make a diagnosis.

Seek emergency treatment if you develop any signs or symptoms of anaphylaxis, such as:

*Constriction of airways that makes it difficult to breathe
*Shock, with a severe drop in blood pressure
*Rapid pulse
*Dizziness or lightheadedness

How we diagnose an allergy

• Take a detailed history: Look for genetic and lifestyle risk factors for food allergies. Your history takes into account foods you are eating—because that’s where the culprit is likely to be. For example, in the United States, wheat allergy is much more common than in China, because we eat so much pizza, pasta and bread. In China, the number one food allergy is, you guessed it, rice.
• Rule out sensitivity to food: This is different than a true allergy and often confused. There are various common food sensitivities including lactose intolerance, gluten sensitivity (in severe cases, it’s called Celiac disease) and gastrointestinal reflux (GERD). The symptoms tend to be different and can include digestive problems like gas and pain, nausea, as well as itching, or even joint pain, headaches, rashes and anemia.
• Testing for food allergies: This can be done in two ways. One of the older ways is called skin-prick testing. This is where a drop of a liquid allergen is placed on the surface of the skin and gently pricked with a plastic tooth-pick device. If your skin develops an itchy, red wheal (bump), then this could mean you’re allergic to the particular allergen. This does come with a small risk of having a severe reaction to the allergen.

New advances in testing

The innovative way to test for food allergies is through blood testing. The most precise tests available, called ImmunoCAP and ISAC by Phadia, measure the specific allergen components. The blood is drawn and sent to a lab to be analyzed for levels of individual protein components of the allergen. This is important because being allergic to some protein components is more dangerous than others.

The advantages of blood tests are that they are accurate and safe. You’re not exposed to the allergen, so there’s no risk of having a severe reaction to the test. The ISAC test in particular does precise component testing of specific food and environmental allergens. This gives the advantage of avoiding false cross-reacting positive test, and gives a quantified level of specific allergen.