Allergen Skin Test
The allergen skin test is the most sensitive and accurate test for the detection of allergies. There are two common types of skin testing: epicutaneous testing and intradermal testing.
Epicutaneous testing involves small amounts of allergen being pricked into the superficial layer of skin called the dermis. Allergens which are negative for allergic reactivity by epicutaneous testing require intradermal testing.
Intradermal testing involves injecting large amounts of allergens into a deeper layer of skin called the dermis.
In both types of testing, allergies are identified through the formation of swelling (wheal) and redness (flare) responses at the site of the prick or injection.
Allergen Blood Tests
RAST (radioallergosorbent test) and ELISA (enzyme-linked immunosorbent assay) testing are blood tests used to detect allergen levels in the blood. These tests are not as sensitive as allergen skin testing and generally only used when skin testing is not available or cannot be performed. Other blood tests such as complete blood counts and total serum IgE levels may also be helpful in suggesting the presence of allergies. However these tests do not identify specific allergies.
Nasal cytology or nasal smear involves the microscopic examination of nasal mucus obtained by blowing your nose into plastic wrap or introducing a cotton tipped swab into the nose. Nasal smears are used to differentiate infectious rhinitis from allergic rhinitis.