How allergy testing works
How skin tests work. Your allergist will mark areas of the skin and place a droplet of a solution with the allergen next to each mark, before using a needle to gently prick the allergen extract into the skin. After about 15 minutes, your skin is checked for redness and a wheal (or hive)—signs of an allergic response. If you show a positive reaction to any of the substances applied, you’ll develop a red, itchy bump, which the allergist and their team will measure to gauge your body’s reaction before the marks are washed off.