A black toenail is a common occurrence with various underlying reasons. It signifies a change in the nail’s appearance, often due to bleeding, bruising, or pigment alterations beneath the nail plate. Understanding the potential causes helps determine when to seek professional medical advice and how to address the issue.
Common Reasons for a Black Toenail
The most frequent cause of a black toenail is trauma, resulting in a subungual hematoma. This occurs when an impact, such as stubbing a toe or dropping an object on the foot, causes blood vessels under the nail to break and blood to collect. Repetitive friction from ill-fitting shoes or activities like running can also cause this bruising. The pooled blood appears dark, and the nail may feel tender or painful due to pressure.
Fungal infections, or onychomycosis, can cause toenail discoloration, sometimes appearing black. These infections often begin as white or yellow spots and progress to darker shades as debris accumulates under the nail. Fungi thrive in warm, moist environments, making toenails particularly susceptible.
In rare instances, a black toenail can indicate subungual melanoma, a serious form of skin cancer that develops under the nail. This condition typically appears as a brown or black streak that may widen or change over time, and it is not associated with a known injury. While uncommon, awareness of this possibility is important. Benign nevi, or moles, located under the nail can also cause a dark streak, which is a non-cancerous pigmentation.
Certain medications can lead to nail discoloration as a side effect. Some systemic diseases can also affect nail health and color. Conditions like diabetes, kidney disease, or circulatory problems can impact nail appearance. These underlying health issues may make individuals more prone to nail changes or complications.
When to See a Doctor
Seek medical attention for a black toenail under several circumstances. If discoloration appears without clear trauma, or if it persists or worsens over time, a professional evaluation is recommended. Signs of infection, such as increasing pain, swelling, redness, warmth, or pus, warrant prompt medical assessment.
A dark streak extending to the cuticle or surrounding skin, known as Hutchinson’s sign, is concerning for subungual melanoma. If multiple nails are affected without clear trauma, or if the black area is rapidly growing or changing, seek medical consultation. Any significant pain or pressure under the nail that does not subside also warrants a healthcare visit.
Medical Evaluation and Care
Medical evaluation for a black toenail typically begins with a physical examination and patient history review. The doctor will inquire about any recent injuries, the onset of discoloration, and other associated symptoms. Depending on the suspected cause, various diagnostic tests may be performed.
For a suspected fungal infection, the doctor might take a nail clipping or scrape debris for a fungal culture. If subungual melanoma is a concern, a biopsy of the affected nail area is often necessary to check for cancerous changes. In cases of severe trauma, an X-ray might be ordered to rule out underlying bone fractures.
Treatment options vary based on the diagnosis. For a subungual hematoma causing pain, trephination may be performed to drain pooled blood, relieving pressure. This procedure is most effective if done within 48 hours of injury.
Fungal infections are typically treated with antifungal medications, which can be topical or oral, often requiring several months of use. Subungual melanoma usually requires surgical removal of the affected nail and surrounding tissue, and in advanced cases, amputation might be considered. Benign conditions like a mole under the nail require observation.
Preventing Black Toenails
Preventing black toenails often involves simple adjustments to footwear and foot care practices. Wearing properly fitting shoes is key, ensuring ample space in the toe box to prevent compression or repetitive friction. Shoes that are too tight or too loose can both contribute to trauma.
Regular and correct toenail trimming is important. Toenails should be trimmed straight across, not too short, to prevent hitting shoes or causing pressure. Protecting feet during activities that might cause trauma, such as wearing appropriate footwear during sports or when handling heavy objects, reduces injury risk. Maintaining good foot hygiene, including keeping feet dry and wearing breathable footwear and moisture-wicking socks, helps prevent fungal infections.