The sudden redness and swelling of the thumb may have several causes: 1. Gout. Most patients with gout have sudden redness and swelling of the thumb root as the first symptom, which can be accompanied by pain, increased skin temperature, and in severe cases, the formation of gout stones, which requires blood uric acid tests for further diagnosis and treatment, and if diagnosed, early treatment with uric acid-lowering drugs. 2. Infection of the soft tissue of the skin. In this case, localized redness and swelling can also occur, accompanied by increased skin temperature and obvious pressure pain, limited movement of the toes, requiring blood tests and radiographs to rule out other diseases. 3, finally, bone tuberculosis or soft tissue tuberculosis, resulting in sudden redness and swelling of the thumb, often accompanied by systemic symptoms, such as low fever, loss of appetite, night sweats, wasting and other symptoms, to be X-rayed, CTed, and if necessary, nuclear medicine, X-rays, CT and, if necessary, MRI, and blood tests related to tuberculosis should be performed to further confirm the diagnosis.