Intradermal injections are used primarily for skin testing. Because these drugs are very strong, they are injected into the outer layer of the skin where the blood supply is less. And the drug will be absorbed more slowly into the blood. The needle is inserted at 5-15 degree angle, pushed about 1/8th of an inch through the skin and the medicine is injected very slowly. Normally the skin will swell slightly where the needle was inserted. The needle is then withdrawn.