The tuberculosis skin test is used to check for tuberculosis infection by observing the redness and swelling of the skin for 72 hours after injection and measuring the diameter of the nodules to determine if they are infected. Therefore, if the skin test for tuberculosis is red and swollen, it is necessary to determine whether it is normal in combination with the diameter of the nodules that appear. If the diameter of hard nodules is <5mm, it is negative and normal, suggesting no infection of TB bacilli; if the diameter of hard nodules is >5mm and <15mm, it is positive, among which >5mm in patients who have not received BCG vaccine suggests infection, and >10mm in patients who have received BCG vaccine suggests infection; if the diameter of hard nodules is >15mm or symptoms such as redness, swelling and ulceration appear in the skin test area, it is strongly positive If the nodules are >15mm in diameter or if there are symptoms such as redness, swelling or ulceration in the skin test area, it is a strong positive indication of TB infection. If the test is positive or strongly positive, the patient needs to go to a specialized TB hospital for treatment. It is important to avoid touching, squeezing or scratching the skin test site during this period. It is also important to avoid eating spicy or seafood foods and avoid splashing water or other liquids on the skin test site, which can cause inaccurate skin test results.