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Tired of Guessing What You’re Allergic To?

Allergy image

Finding out what you are allergic to is an important first step to effectively manage your allergic condition. Allergy tests are convenient and accurate. When combined with a detailed medical history, allergy testing can help find the specific cause of your allergic reactions.

Allergy tests should be performed by allergists, who are specialists trained in the best methods for testing and treating allergies.

Who can be tested for allergies?
Adults and young children can be tested for allergies. Your allergist knows which kind of test is suitable for each age group.

How do allergy skin tests work?
Allergy testing can be done as skin tests or as blood tests. There are two types of skin tests.

Allergy testing can help find the specific cause of your allergic reactions.

During the first type of skin test, a drop of a suspected allergen is pricked on the surface of the skin. The test is performed on the back or forearm. Many suspected allergens can be tested at the same time. Sometimes only a small number of selected allergens is necessary. If you have redness and swelling at the test spot, then you might be allergic to this allergen. Your allergist will help to interpret this result.

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 forearm. Several suspected allergens can be 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 appear within 20 minutes. Sometimes redness and swelling can occur several hours after skin testing, and usually disappear in 24 to 48 hours. Delayed reactions do not correlate with allergy, but should be reported to the allergist or nurse.

Is skin testing painful?
Both types of skin tests have little or no pain. However, positive reactions cause itchy red bumps that look and feel like mosquito bites. The itching and bumps are usually gone in just a few minutes or, rarely, in hours.

Does medicine interfere with allergy skin tests?
Some medicines do interfere with allergy skin tests. Your doctor 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 person being tested is taking a medicine that can interfere with skin testing, but cannot be stopped for a few days.
  • The person has a severe skin condition such as eczema or psoriasis.
  • Skin testing a highly sensitive person may cause a very large reaction.
  • For babies and very young children, a single needle stick for allergy blood testing may be simpler than several skin tests.

Which test method is best?
Skin tests give fast results. They usually cost less than allergy blood tests. However, some medicines can interfere with skin tests. In addition, it may be hard to read the tests in some people with dark skin. Also, the skill of the tester may affect the results. Therefore, the test should be done by a person with special training.

Blood tests are helpful because they involve a single needle prick. Medicine does not interfere with the results of a blood test. Because the blood sample must be sent to a lab for testing, it takes several days to get the results. Blood tests cost more than skin tests. There are many 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 your medical history.

Are there risks or side effects from allergy testing?
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 done. In rare cases, a more serious reaction can occur. That is why skin tests should be done by an allergist. The risk with allergy blood tests is pain or bleeding where the needle enters the skin. Also, some people may feel dizzy or faint during blood testing.

What allergies can allergy testing find?
Allergy tests help find allergies to pollen, molds, dust mites, animal allergens, insect stings, foods, and some medicines.

Does a positive allergy test mean that I am allergic?
A positive result does not always mean that you are allergic to that allergen. It is, therefore, important to have testing performed by an allergist. These specialists will carefully select which tests to perform and correlate these results with your clinical history. This will determine which results apply to your allergic condition.


Source: American College of Allergy, Asthma & Immunology,

This article was originally published in Coping® with Allergies & Asthma magazine, Spring/Summer 2011.