What is a Black Toenail? “Black Toenail” is other wise called as a Runner’s Toenail which is nothing but when the accumulation of blood under the nail plate and the blood which deposits under the nail which means that the hemosiderin which is a black color material that is due to the blood beneath which cause it to the toenail so it is called a Black Toenail. What is a Black Toenail...