What is a "scratch test" and an "intradermal test"?

What is a "scratch test" and an "intradermal test"?

Harold Kaiser (Practicing Allergist and Clinical Professor of Medicine, University of Minnesota Medical School) gives expert video advice on: When should I see a doctor if I think I have allergies?; Are allergies genetic?; What are the tests to find out if I have allergies? and more...

Intradermal means in the skin and allergy skin tests are typically either scratch tests or intradermal. A scratch test means, as the name implies, a scratch is made on the skin and potential allergens, again think of grass pollen or dust or cat dander, is applied to the scratch. In about fifteen to twenty minutes, if the patient is having an allergic reaction, you will get a redness which we call a wheel and flare reaction which indicates a positive reaction. If there is a positive reaction, then one can assume that the potential that this indicates an allergy is present is there. Now, some patients don't react to the scratch test and they need a stronger test. A stronger test means the same substance is injected with a needle intra the skin, or intradermally, and for some patients it's necessary to get to that stronger test to get an answer.