The TB skin test usually begins to react locally in about two days, and the results usually need to be seen at three days to determine if it is positive. The TB skin test, commonly referred to as the PPD test, is a test to determine tuberculosis infection. It is usually necessary to wait three days after a localized PPD skin test to read the results of the test. So, if the skin test is positive, a reaction is expected at three days. Although the reaction to the TB skin test is most noticeable at about three days, the reaction to the TB skin test may start earlier, sometimes at about two days. In mild cases, there may be localized hard nodules, and in severe cases, there may be visible blisters. After PPD skin test, do not scratch the local area, so as not to affect the results; when the skin test reaction is obvious, we need to focus on checking for acute tuberculosis infection, and actively deal with it.