There are many causes of black or dark toenails, but the most common cause is trauma (injury). When an injury results in nail discoloration it is referred to as a subungual hematoma, which simply means there is a collection of blood underneath the nail.
This collection not only causes the nail to become discolored, it also generates pressure, usually leading to pain. In many cases, medical treatment is advised not only to relieve this discomfort, but to remove the entire nail and examine the nail bed for significant laceration or exposed bone.
Although everyone is susceptible to black toenails resulting from accidental trauma, athletes and those who often walk barefoot are at a higher risk. Black toenails can also be caused by a fungal infection, or may indicate underlying melanoma (a malignant tumor consisting of dark-pigmented cells called melanocytes).
Often, a black toenail will eventually fall off and regenerate on its own. If pain or signs of infection (such as pus, discharge, foul odour, fevers or chills) are not present, you may not need to seek medical treatment right away. Even so, keep in mind that when the nail returns it may be abnormal as a result of the trauma. Furthermore, if at any time the discoloration covers more than a quarter 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; this can make your toes and feet susceptible to injury or trauma.
- Keep feet and nails clean and dry.
- Always wear clean socks and shoes.
- Treat any nail problems during their early stages.