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Allergies Health Center

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Food Allergies: 5 Myths Debunked

How to tell a food allergy from an intolerance or sensitivity -- and what to do about it.

Myth: I only need a blood test to diagnose a food allergy.

Blood tests can also help diagnose a true food allergy by measuring IgE levels and determine whether there’s a true food allergy. However, the new guidelines recommend against the routine use of these tests and making a food allergy diagnosis based on them alone.

Fleischer warns that blood tests can produce false-positives -- results that indicate an allergy when there isn't one -- in patients who have eczema, asthma, or other types of allergies because those people already have higher-than-average IgE levels.

One accurate way to find out if you have a true food allergy is to visit your doctor and undergo a food challenge, says David Fleischer, MD, a pediatric allergist at National Jewish Health in Denver.

The food challenge is managed by the doctor and done in a controlled environment at the doctor’s office. It involves gradually giving higher doses of a particular food to see how much of that food is needed to trigger an immune system response.

Another type of test -- the skin prick test -- can also indicate if the patient has a real food allergy by injecting a small amount of the allergen into the skin and checking whether the skin develops a bump or a rash. Again, an allergy diagnosis should not be made on a skin test alone.

Food elimination diets -- taking away one or a few specific foods to see if the reaction disappears -- may help.

Myth: I can easily tell which foods trigger my allergies.

Reality: You might need to do more work than you think to spot all your trigger ingredients.

The 2004 Food Allergen Labeling and Consumer Protection Act made it easier to read food labels and quickly determine what’s safe to eat and what isn't. The federal law requires warnings written in plain English for the eight most threatening food allergens: wheat, soy, milk, peanut, tree nut, shellfish, fish, and egg.

However, there is still risk, because a manufacturer “cannot ensure 100% that there are not traces of the food allergen in their product," Burks says.

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