A skin test is a medical procedure used to determine if a person has an allergic reaction to a specific substance, such as pollen, pet dander, or certain foods. During the test, a small amount of the allergen is introduced to the skin, usually through a prick or scratch. The area is then monitored for any signs of an allergic response, such as redness or swelling. Skin tests can also be used to check for infections, like those caused by tuberculosis. In this case, a small amount of a test substance is injected under the skin, and the reaction is evaluated after a couple of days. These tests help healthcare providers diagnose allergies and infections effectively.