Whether or not a TB skin test with redness is normal is determined by the size of the diameter of the redness, which may or may not be normal.
TB skin test is mainly used to check whether the infection of tuberculosis is a way, usually 72 hours after the injection to observe whether the skin appears red and swollen, by measuring the diameter of the red and swollen to initially determine whether there is an infection. If the diameter of the redness is less than 5mm, it means negative, which is generally normal.
If the diameter of the red swelling is 5-15mm, it is positive. For patients who have not been vaccinated with BCG, a diameter of the red swelling greater than 5mm suggests that there is an infection, which is abnormal. For patients who have been vaccinated with BCG, a red swelling with a diameter greater than 10 mm is indicative of an infection. When the diameter of the red swelling is greater than 15mm, it indicates a strong positive, highly suggestive of infection, which is an abnormal phenomenon.
If the diameter of the red swelling is greater than 5mm, it is recommended to go to a specialized hospital for further examination and treatment under the guidance of a doctor.