The thickening and blackening of bunions on the feet is often caused by the following reasons: first, local trauma, when the toe is traumatized will lead to rupture of the blood vessels inside the nail, it will be black in color, generally do not worry too much, you can locally rub iodophor or Bactrim and other topical drugs to anti-infection treatment. You can also eat foods that help you recover, such as green vegetables, or fruits rich in B vitamins and C vitamins, such as kiwi, apple, banana, duck pear, etc. Second, sometimes it is also caused by local infection, you need to go to the hospital surgery for treatment, the doctor will give local debridement according to the condition, if necessary, you also need to remove the nail to eradicate, and later to change the medicine treatment. The nail should not be exposed to water for a short period of time to prevent infection. It is also necessary to consume foods rich in unsaturated fatty acids, such as walnuts and peanuts, to help the local recovery.