While the double-blind strategy is useful and practical for mild allergic reactions, it must be done carefully in individuals with suspected severe reactions to foods. Blood tests may be a safer first approach.
BLOOD TESTS
Blood tests can be done to measure the amount of immunoglobulin (Ig) E
Other blood tests include:
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Absolute eosinophil count - Total IgE level
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Serum immunoglobulin electrophoresis
PROVOCATION
Provocation (challenge) testing involves exposing a person to a suspected allergen under controlled circumstances. This may be done in the diet or by breathing in the suspected allergen. This type of test may provoke severe allergic reactions. Challenge testing should only be done by a doctor.
How to prepare for the test
Before any allergy testing, the health care provider will ask for a very detailed medical history. This may include questions about such things as illnesses, emotional and social conditions, work, entertainment, lifestyle, foods, and eating habits.
If skin testing will be performed, you should NOT take antihistamines before the test. This may lead to a false-negative result, falsely reassuring you that a substance is unlikely to cause a severe allergic reaction. Your doctor will tell you which medicines to avoid and when to stop taking them before the test.
How the test will feel
Skin tests may cause very mild discomfort when the skin is pricked. Itching may occur if you have a positive reaction to the allergen.
Why the test is performed
Allergy tests are done to determine the specific substances that cause an allergic reaction in a person.
Your doctor may order allergy tests if you have:
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Allergic rhinitis and asthma symptoms that are not easily controlled with medications -
Angioedema and hives - Food allergies
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Contact dermatitis - Penicillin allergy*
*NOTE: Allergies to penicillin and closely related medications are the only drug allergies that can be tested using skin tests. Skin tests for allergies to other drugs can be dangerous.
The prick skin test may also be used to diagnose food allergies. Intradermal tests are not used to test for food allergies because of high false positive results and the danger of causing a severe allergic reaction.
