Redness and swelling after TB skin test is normal, redness and swelling is not a criterion for determining whether there is an infection or not, just pay attention to avoid infection. Redness and swelling are normal after a TB skin test, so there is no need to worry too much. The criterion for determining whether an infection is present is not the presence of redness and swelling, but the size of the nodules, which are defined as positive only if the diameter of the nodules is greater than 5mm, and need to be combined with other test results and clinical symptoms to confirm the diagnosis. Therefore, redness and swelling are normal reactions of the skin, especially for people with allergies. Care should be taken to avoid scratching, which can lead to ulceration and subsequent infection. At the same time, avoid soapy water and other local stimulation, the emergence of pus and other infectious manifestations, need to consult a doctor in a timely manner.