The whitening of the thumb may be caused by trauma, or anemia, nail fungus, other diseases. 1. Trauma: If you don’t trim your toenails in time, coupled with recent foot pressure injuries from heavy objects, to a certain extent, you are prone to the condition of white toenails. 2. Anemia: the cause of this disease can be broadly divided into three aspects, namely, insufficient or reduced red blood cell production, excessive destruction of red blood cells and excessive blood loss. These include dietary imbalance, prolonged exposure to radiation, viral infections and so on. When the body anemia will reduce the blood supply of the peripheral microcirculation of the extremities, which will appear in the case of whitening of the nail beds, manifested as whitening of the thumbs of the feet. 3. ringworm of the nail: the disease is caused by the skin ringworm infection, or by ringworm direct infection, can be triggered by nail trauma, lymphatic circulation disorders, immune impaired state and other factors, in the early stage of the nails are mostly white, yellow, so the patient will appear the performance of the feet thumb white. 4. Other: clinically, we also need to consider the possibility of psoriasis, cirrhosis, nephrotic syndrome and other diseases caused by the whitening of the thumbs. It is recommended that patients with white thumbs go to the hospital to improve the relevant examinations to clarify the specific causes.