An intradermal skin test may be done when a substance does not cause a reaction in the skin prick test but is still suspected to be an allergen for that person. During this test, a small amount of the allergen solution is injected into the skin under its top-most layer. The intradermal test is more sensitive than the skin prick test but can be slightly more uncomfortable. A positive result is a swelling of more than 3mm in diameter.
Intradermal Skin Tests