The only time anti-tuberculosis treatment is needed is when there is active tuberculosis with bacteria in the sputum. TB infection can be determined by the TB test, also known as the PPD test, in which a combination of toxins is injected into the skin and the skin is observed for changes after 48-72 hours. If the skin does not show obvious nodules, only redness or very small nodules with a diameter of <5mm is negative, a negative test means that the skin has not been infected with Mycobacterium tuberculosis and BCG vaccine can be injected to avoid infection with Mycobacterium tuberculosis. If the nodule is >5mm in diameter, it is positive, and positive means that it is infected with Mycobacterium tuberculosis. If the diameter is >2 cm, it is strongly positive, and a strong positive is meaningful for the diagnosis of active tuberculosis.