Our Public Health Clinics offer Low-cost TB testing and clearance to meet school and employment requirements. The TB skin test (also called the Mantoux tuberculin skin test) is performed by injecting a small amount of fluid (called tuberculin) into the skin in the lower part of the arm. A person given the tuberculin skin test must return within 48 to 72 hours to the clinic to have a clinician looking for a reaction on the arm. The clinician will look for a raised, hard area or swelling, and if present, measure its size using a ruler. Redness by itself is not considered part of the reaction.