There are many causes of black or dark toenails, but the most common cause is some kind of injury that causes blood to collect underneath the nail. This collection not only causes the nail to become discoloured, it also generates pressure, usually resulting in pain.
Although this type of toe injury can happen to anyone, athletes and those who often walk barefoot are at a higher risk. Black toenails can also be caused by a fungal infection, or may be a sign of an underlying melanoma (a malignant tumour consisting of dark-pigmented cells called melanocytes).
Often, a black toenail will eventually fall off and re-grow without treatment. If pain or signs of infection aren’t present, you may not need to seek medical treatment immediately. But keep in mind that when the nail returns, it may be abnormal. Also, if at any time the discoloration covers a significant part (a quarter or more) of the nail, medical attention should be sought. This is because, in such cases, it is likely that the nail bed itself is damaged, or that there is exposed bone under the nail. If left untreated, this condition can lead to a bone infection (osteomyelitis).
The following will help to prevent black toenails:
- Keep toenails trimmed properly - not too short and straight across.
- Wear properly fitting shoes.
- Try to avoid walking barefoot.
- Keep feet and nails clean and dry.
- Treat any nail problems during their early stages.