There could be several reasons for toenails turning black.
The most common reason, especially among those who are regularly running, hiking, or playing sports is repetitive trauma against the toe, often from shoes that are too tight. This can cause cuts or bruises under the nail, leading to a pooling of blood that causes the distinct discoloration. Black toenails may also be caused by a fungal infection, as well.
More rarely, a black toenail might be the result of a malignant melanoma, an aggressive form of skin cancer. Although the odds of this being the case are very low, you should definitely investigate if you have any concerns—diagnosing and treating melanoma as early as possible is critical to achieve a good outcome, so you’ll want a professional evaluation to either rule it out or begin countermeasures quickly.
If you have any concerns with the color or health of your toenails, please schedule an appointment with Dr. McSpadden at North Austin Foot & Ankle Institute, in our Cedar Park or Round Rock offices. You can reach us online, or give us a call at 512-593-2949.