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Tuberculin Skin Test


A tuberculin skin test is done to see if you are infected with the bacteria that cause tuberculosis (TB). Tuberculin is a liquid that healthcare providers inject into the skin of your arm. Your skin will react to tuberculin if you are infected. TB is a serious infection that usually starts in the lungs. The bacteria are easily spread from one person to another through the air. They can live in your body a long time without making you sick. This is called latent TB. Latent TB can develop into active TB if it is not treated.


Seek care immediately if:

  • You have chest pain.
  • You have a mild cough that gets worse. You may cough up white, yellow blood-streaked sputum.
  • You have blisters, ulcers, or your skin has turned black in the injection area.
  • Your skin is itchy, or you have a rash or hives that are spreading.
  • Your face is red and swollen.
  • Your mouth is swollen, your throat feels tight, or you have trouble breathing.

Contact your healthcare provider if:

  • You have questions or concerns about the test or about TB.

After the test:

  • Return in 2 to 3 days. Your skin must be checked 2 to 3 days after the test. You will need another TB skin test if you do not come back within 3 days.
  • Watch for signs of allergic reaction. Some people have an allergic reaction to tuberculin. Seek care immediately if you have any symptoms of allergic reaction, such as hives or swelling.

What the test results mean:

The TB skin test can only show that you were infected with the germ that causes tuberculosis. You will need more tests to learn if you have latent or active TB. The most common tests are chest x-rays and sputum samples.

  • Your test is positive if the area around the skin test is raised or hard. Your test can be positive even if you do not have active TB. This would happen if you received a BCG vaccination for TB.
  • Your test is negative if there is no change to your skin. Your test can be negative even if you do have TB. Your immune system may be too weak to react to the tuberculin, or you may have been exposed too recently.

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The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.