Allergy Testing

Allergy testing can be administered in two ways: via skin or blood test. It is done to determine the substance or allergen that a person may be allergic to. Skin tests are the most common allergy testing method since it yields fast result and it is inexpensive. However, blood tests may also be used as an alternative to skin tests.

Skin allergy testing

Skin test is done by using a tiny amount of a suspected allergen. It is injected just below the person's skin to check if any allergic reaction will develop.

3 types of skin tests:

• Skin prick test - is done by inserting, via tiny scratch or needle pricks, a droplet of allergen solution into the skin. A tiny red, itchy bump or swelling will develop if the person is allergic to the allergen. This is referred to as positive reaction.

• Intradermal test - is almost the same as the skin prick test, only that it involves actual injection of the allergen solution into the skin. Intradermal test is usually done when the skin prick test does not sufficiently yield the desired result or does not cause any reaction to the skin. Intradermal test is more sensitive.

• Skin patch test - involves placing the allergen solution on a pad which is taped and left on the skin for 24-72 hours. This test is particularly used for the detection of contact dermatitis which is a type of skin allergy.

Blood test

Blood test is done to measure the amount of antibodies. It is not as sensitive as skin tests, but it is used for patients who are not suitable for skin tests.

The ELISA or EIA are types of enzyme-linked immunosorbent assay. This test measures the IgE in the patient's blood. IgE stands for immunoglobulin E - an antibody that the body creates in response to particular allergens. People with allergies or asthma have high levels of IgE.

Other lab tests

Other laboratory allergy tests include: RAST or radioallergosorbent testing, and immunoassay capture test [i.e. UniCAP, Pharmacia CAP or ImmunoCAP]. These tests may be used as back-up tests.

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