This medicine is used to prevent any activation of the infection in the future, but you are not infectious to others. If you have a positive skin test and an abnormal chest radiograph or symptoms of tuberculosis, you'll be treated for active disease. When you're diagnosed with active disease, you're infectious to others. You may be treated with 3 or 4 medicines for 9 to 12 months. You'll need to take precautions with your family, and you'll be kept out of work until you're no longer infectious.
Active tuberculosis is much less common than skin test conversion.
If in the past you received BCG vaccine to prevent tuberculosis, you may have a mild reaction to the tuberculosis skin test, but you should still be tested. Usually, BCG reactions related to the tuberculosis skin test become less severe over time. If your skin test increases in size and intensity, it may indicate that you have been infected with tuberculosis, and you need to be treated. Unless you recently had your yearly tuberculosis test, you should have a baseline tuberculosis skin test if you are exposed to a patient with active tuberculosis, especially if the disease wasn't recognized, and isolation and masks were not used. A follow-up test in 3 months will show if the exposure resulted in infection.