Allergy skin testing is a diagnostic tool that can be done to find out for sure if you have allergies, and, if you do, to discover what you are allergic to. Although it is also possible to do blood tests for allergies, the most reliable testing for allergies is done by introducing extracts of tiny amounts of substances to which you might be allergic into the surface of your skin.
If your immune system has produced allergic antibodies, some of them will be attached to so-called “mast cells” in your skin. And even if your allergies don’t cause rashes or hives, localized reactions similar to mosquito bites will appear where your skin is pricked with extracts of substances to which you are allergic.
A number of extracts are usually used and those to which you react are your particular allergens. Extracts of substances to which you are not allergic won’t cause a significant reaction on your skin.