Black Toenail: Common Causes
If your toenail turns black, it’s most likely a bruise under the nail, technically called a subungual hematoma. You can get it from stubbing a toe or from footwear that cram your feet into the front of the shoe. The bruise usually starts out red, then becomes purple, dark brown, and finally black when blood beneath the nail pools and clots. Expect your black toenail to grow out in about 6 to 9 months or longer.