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Allergy Testing

More than 50 million people in the United States have allergies. Finding out what you are allergic to is an important first step to effective allergy treatment. Today allergy tests are more convenient and accurate than ever before. When combined with a detailed medical history, allergy testing can identify the specific things that trigger your allergic reactions.

Are there any allergy testing side effects?

Any medical test involves some risk. The risk with allergy skin tests is that allergy symptoms might occur during the test. The most common symptoms are itching and swelling of the skin where the tests are. In rare cases, a more serious reaction can occur. That is why skin tests should be done by a specialist. The risk with allergy blood tests is pain or bleeding at the needle mark. Also, a few people may faint during blood testing.

What about allergy testing in children? Who can be tested for allergies?

Adults and children of any age can be tested for allergies.

How is allergy testing done?

Allergy testing can be done as skin tests or as blood tests. Usually, allergy tests are done under the guidance of an allergy specialist. These specialists are trained in the best methods for testing and treating allergies.

How do allergy skin tests work?

There are two types of skin tests. During the first type of skin test, a drop of a suspected allergen is pricked or scratched on the surface of the skin. The test is performed on the back or forearm. Many suspected allergens are tested at the same time. If you are allergic to one of the tests, you will have redness and swelling at the test spot.

Sometimes the doctor will recommend a second type of test. In this type, a small amount of the suspected allergen is injected into the skin of the arm or forearm. Several suspected allergens are tested at the same time.

How long does it take to get skin test results?

Skin testing is fast. For both types of skin tests, positive reactions usually appear within 20 minutes. Sometimes redness and swelling can occur several hours after skin testing. The delayed reaction usually disappears in 24 to 48 hours, but should be reported to the allergy doctor or nurse.

Is skin testing painful?

Both types of skin tests have little or no pain. However, positive reactions cause annoying itching red bumps which look and feel like mosquito bites. The itching and bumps are gone usually in just a few short minutes or hours.

Does medicine interfere with allergy skin tests?

Some medicines do interfere with allergy skin tests. The allergist will tell you if you have to change your medicine before allergy skin testing.

When are allergy blood tests used?

An allergy blood test is often used because:

  • The patient is taking a medicine that can interfere with skin testing, but cannot be stopped for a few days
  • The patient suffers from a severe skin condition such as eczema or psoriasis
  • Testing with a strong allergen might cause an extra large positive reaction
  • For babies and very young children, a single needle stick for allergy blood testing may be better than several skin tests.

How long does it take to get blood test results?

Because the blood sample must be sent to a lab for testing, it takes many days to get the results.

Which test method is best?

Skin tests give fast results. They usually cost less than allergy blood tests. What are the negatives? Young children do not like this type of test. Some medicines can interfere with the tests. In addition, in some people with dark skin it may be hard to read the tests. Also, the skill of the tester may affect the results. The test should be done by a person with lots of training.

Blood tests are helpful because they involve a single needle prick. Medicine does not interfere with the results. However, it takes a long time to get the results. Blood tests cost more than skin tests. There are many of types of allergy blood tests. Some types are more helpful than others.

Each test method has pluses and minuses. The test results alone do not diagnose allergies. All test results, from either type of test, must be interpreted together with the medical history.

What allergies can allergy testing find?

A blood test for allergies can help find allergies to pollen, molds, dust mites, animal dander, insect stings, foods and some medicines.

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