What should you know about the tuberculin Mantoux skin test?

A small amount of tuberculin is placed just under the skin, usually on the forearm. The clinician does not judge the result by redness alone; they assess the firm raised area and consider your age, health, vaccination history, exposure and reason for testing. A positive result suggests immune sensitisation, but it does not by itself prove active tuberculosis. Further assessment may include symptoms, examination, a chest X-ray or another test.

Tell the testing team about previous tuberculosis infection, a past Mantoux result, tuberculosis vaccination, immune-suppressing treatment and any recent exposure. Keep the site clean and avoid scratching or covering it with irritating products. Return when instructed so the skin can be examined; a reading done too early or too late may not answer the question reliably. Bring any requested records to the appointment.

Contact the testing service if the site becomes very painful, develops marked swelling, blisters or an open sore, or if you feel unwell after the injection. Seek prompt medical advice for persistent cough, coughing blood, unexplained weight loss, night sweats, fever or close contact with someone who has tuberculosis. These symptoms need clinical assessment regardless of a skin-test result.

Ask why the test is recommended, when it must be read, how vaccination or immune treatment affects interpretation, and whether you need a chest X-ray or another tuberculosis screening test.