Intradermal test is one of the diagnostic tests done in allergies. It is similar to skin prick test except that here the allergen is injected under the surface of the skin. In skin prick test the allergen is put on the skin and skin is pricked to see the reaction of the skin towards the allergen. In intradermal test the allergen is introduced under the skin.
Intradermal test is done after skin prick test, when there are no satisfactory results for skin prick test. Sometimes it happens that a substance is suspected as an allergen for the patient. Skin prick test is done but there are no reactionary symptoms that are clear enough to confirm it as an allergen.
In such cases, the allergen is placed underneath the skin, hence it is called intradermal test. This test is more sensitive than the skin prick test. It is more often positive in people who do not have symptoms to that allergen in skin prick test. Thus it is called false-positive test
Definition of false-positive test result:
A false-positive test result is the test that is done to detect a condition or a disease when it is not present. This may suggest that a person has the condition when he or she does not. For example, in pregnancy test human chorionic gonadotropin is detected. The false positive result appears to detect it when in reality the woman is not pregnant.
Skin prick test and intradermal test are done to:
- To know whether the person is allergic to certain allergens or not.
- To measure specific IgE attached to mast cells in the skin.
- To identify food allergens such as milk, eggs, peanuts, soy, wheat etc.
- To identify airborne allergens that are inhaled. For example: pollen, trees, shrub, molds, dust, feathers, pet danders and others.
- To determine whether a patient is allergic to a medicine or insect venom.
