Clear, healthy nails are an ideal in society, which is why so much time and money are spent each year keeping many at peak appearance. Yet regardless of whether someone goes the extra mile for pedicures and treatments, it can be troubling to see a once normal nail suddenly grow darkened. A black toenail can result from several different causes, with the proper treatment often depending on the reason for the blackout.
Reasons for a Black Toenail
Minor repetitive trauma is one of the most common causes of black toenails, often as the result of the toes striking the inside of the shoe. Runners who perform at a high frequency and intensity are at a higher risk of having a black toenail, and the condition is even seen as an odd badge of honor in some running communities. The continuous force of the toes sliding up against the shoe causes the bruising or light bleeding that results in the discoloration, and causes no pain in most cases.
More severe trauma, of course, can be an entirely different matter. The force of a heavy object dropped on the toe can cause a pool of blood to accumulate beneath the nail. This is known as subungual hematoma, and the pressure that builds under the nail can cause a severe, throbbing pain in addition to a blackened nail.
Non-trauma causes of a black toenail can include a fungal infection. This can sometimes cause pain, but not the throbbing type that comes with a severe impact. In much rarer instances, melanoma can cause a dark spot to appear beneath a toenail.