Allergy Testing

If you suspect you have a food allergy, your allergist will typically recommend one of several types of tests to determine if you are allergic to a specific food, such as wheat, soy, milk, nuts, fish or shellfish.

Most people will undergo an allergy skin test. During this test, a small drop of purified food extract is placed on the skin to see if your skin has a reaction. If you have over-reactive skin or eczema, skin testing may produce a false positive reaction, in which case you may need a blood test.

Depending on the test results, further testing may be needed, including:

• An elimination diet that cuts the suspected food out of your diet to see if there is a change in your symptoms.
• An in-office food allergy challenge. Common foods that are used in a food challenge include cow milk, eggs, wheat, peanuts, nuts and shellfish.

You will be asked to bring in the specific food for the challenge. During the food allergy challenge, the food is given in increasing amounts every 20 minutes. After the last dose, a longer observation period is required to ensure there is not a late reaction. If a late reaction occurs, you may be required to remain in the office until the reaction resolves.

Skin testing is a diagnostic test to determine if someone is allergic to common airborne allergen. During the procedure, small drops of purified extracts are placed on the upper back or forearm, and the surface of the skin is poked with a sterile plastic device. After 15 minutes, the skin is examined for swelling and redness at the poke site.

Patch testing is a weeklong test performed to diagnose allergic skin conditions. On the first day, 28 different substances are applied to the upper back and secured with tape. The areas where the substances were applied are then monitored for any reaction. The allergens on the test panel include:

• Metals
• Topical antibiotics
• Preservatives
• Fragrances