A black toenail indicates a change in the color of the toenail to darker shades. This common issue can stem from various causes, from minor conditions to more serious health concerns. Understanding these reasons is important for effective treatment.
Common Reasons for Discoloration
The most frequent cause of a black toenail is a subungual hematoma, or bleeding under the nail plate. This often results from trauma, such as dropping a heavy object on the toe or stubbing it. Repetitive impact, like that experienced by runners or athletes due to ill-fitting shoes or long-distance activities, can also lead to this condition, sometimes called “runner’s toe.” When blood vessels beneath the nail are injured, blood leaks and becomes trapped, causing the nail to appear red or purple initially, then darkening to brown or black as it clots.
Another common reason for toenail discoloration is a fungal infection. These infections occur when fungi enter through cracks in the nail or skin. While less commonly pure black, fungal infections can cause the nail to appear white, yellow, reddish-brown, green, or even black. The discoloration typically starts at the tip of the nail and spreads as the infection progresses, potentially leading to thickening and crumbling of the nail.
Less Common and Serious Underlying Causes
While trauma and fungal infections account for many black toenails, other less common but more serious conditions can also cause discoloration. One such concern is subungual melanoma, a rare but aggressive form of skin cancer that develops under the nail. Unlike a subungual hematoma, which typically arises from an injury, subungual melanoma often appears as a dark, vertical streak or band on the nail that may widen or change over time, and it may not be associated with trauma. The discoloration can be uneven and extend to the surrounding skin, a sign called Hutchinson’s sign.
Certain medications can also lead to nail discoloration. Some chemotherapy agents, for example, can cause the nails to darken. Systemic health conditions may also manifest as changes in nail color. Diseases like kidney disease or certain circulatory problems can impact nail health and lead to discoloration. These less common causes highlight the importance of professional evaluation, especially when a black toenail appears without a clear traumatic event or does not resolve as expected.
When to Seek Professional Medical Advice
Consult a healthcare professional if a black toenail appears without a clear injury or if the discoloration does not improve over time. Medical attention is also warranted if the toenail is accompanied by increasing pain, swelling, or signs of infection such as pus or warmth around the nail. A dark streak that appears suddenly, changes in size, or extends to the skin surrounding the nail should prompt immediate medical evaluation, as these can be indicators of subungual melanoma.
If the nail separates from the nail bed or becomes misshapen, professional assessment is recommended. Individuals with pre-existing conditions like diabetes, circulation problems, or a weakened immune system should seek medical advice for any toenail changes, as they may be at higher risk for complications. A professional evaluation is necessary to determine the underlying cause and ensure appropriate treatment, as self-diagnosis of serious conditions like melanoma is not possible.
Steps to Prevent Toenail Discoloration
Preventing toenail discoloration largely involves minimizing trauma and avoiding fungal infections. Wearing properly fitting shoes is important, particularly for those engaging in activities that involve repetitive foot impact like running. Shoes that are too tight can cause constant pressure on the toes, leading to bleeding under the nail. Selecting breathable footwear can also help prevent fungal growth by reducing moisture around the feet.
Regular and correct toenail trimming is another preventative measure. Nails should be cut straight across and kept short, but not too short, to avoid injury and reduce the risk of ingrown nails or trauma. Using clean nail clippers and avoiding sharing them can prevent the transfer of fungi and bacteria. Wearing protective footwear in public damp areas like showers, locker rooms, and swimming pools also helps prevent fungal exposure. Maintaining good foot hygiene, including daily washing and thorough drying of the feet, especially between the toes, further reduces the risk of fungal infections.