Tuberculin test through the skin test may not have a reaction, or the following reactions may occur, intradermal injection of the skin can appear red spots, as follows: First, if the red spot <5mm is negative, suggesting that there is no infection of tuberculosis, or BCG vaccine injection. If the erythema on the skin is 5-10mm, it is a weak positive result, and it is possible that the skin has been infected with tuberculosis or injected with BCG vaccine. If the erythema is 10-20mm, it indicates a positive result, and it is possible that the skin has been infected with tuberculosis or has been injected with BCG vaccine. Fourth, if the skin test site appears red, swollen, broken, blisters, or > 2cm, suggesting a strong positive result, strong positive patients, may be tuberculosis patients with symptoms.