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How are skin tests used to diagnose food allergies?

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Skin tests are rapid, simple, and relatively safe --although experts don't recommend making a food allergy diagnosis based on skin tests alone. You can have a positive skin test to a food allergen without experiencing allergic reactions to that food. A doctor diagnoses a food allergy only when you have a positive skin test to a specific allergen and the history of these reactions suggests an allergy to the same food.

In some extremely allergic patients who have severe anaphylactic reactions, skin testing cannot be used because it could evoke a dangerous reaction. Skin testing also cannot be done on patients with extensive eczema.

For these patients a doctor may use blood tests such as the RAST and the ELISA. These tests measure the presence of food-specific immunoglobulin E (IgE) in the blood of patients. These tests may cost more than skin tests, and results are not available immediately. As with skin testing, positive tests don't necessarily make the diagnosis.

From: Food Allergy and Food Intolerance WebMD Medical Reference

SOURCES:

The National Institute of Allergy and Infectious Diseases: "Fact Sheet: Food Allergy and Intolerances."  UpToDate. American Academy of Allergy Asthma & Immunology.

Reviewed by Brunilda Nazario on October 29, 2018

SOURCES:

The National Institute of Allergy and Infectious Diseases: "Fact Sheet: Food Allergy and Intolerances."  UpToDate. American Academy of Allergy Asthma & Immunology.

Reviewed by Brunilda Nazario on October 29, 2018

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How is a double-blind food challenge done to diagnose food allergies?

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