A black toenail, or subungual hematoma when caused by trauma, is a dark discoloration beneath the nail plate. The discoloration typically ranges from red to dark purple or black, depending on the cause and the amount of material accumulated. Understanding the underlying reason is important for determining its resolution.
Understanding the Causes
The most frequent cause of a black toenail is trauma, which can range from a single, acute impact to repetitive microtrauma. A direct impact, such as dropping a heavy object on the toe or stubbing it, can rupture small blood vessels underneath the nail. This leads to blood pooling in the confined space between the nail bed and the nail plate, creating the characteristic dark appearance. Repetitive stress, often seen in athletes, can also cause this by continuous friction or pressure from ill-fitting footwear, resulting in minor bleeding over time.
Other causes of toenail discoloration include fungal infections (onychomycosis) and, rarely, subungual melanoma. Fungal infections can cause the nail to thicken, become brittle, and appear dark brown or black due to fungal debris or pigment. Subungual melanoma, a rare form of skin cancer, presents as a dark streak or patch that can spread from the nail bed to the surrounding skin.
The Healing Process and When It Persists
For a black toenail from trauma, the discoloration typically resolves as the nail grows out. The discolored area, essentially dried blood trapped under the nail, gradually moves forward with nail growth. Since toenails grow slowly, this can take 6 to 12 months for the entire discolored portion to be replaced by new, clear nail. No specific intervention is usually required unless pain or pressure is present.
Conversely, a black toenail caused by a fungal infection or subungual melanoma will not resolve on its own. Fungal infections require antifungal treatment, either topical or oral, to eliminate the fungus and allow healthy nail growth. Without treatment, the discoloration and other symptoms, such as thickening and crumbling, will likely persist or worsen. Subungual melanoma, being a cancerous condition, necessitates immediate medical diagnosis and treatment, which often involves surgical removal, as it will not disappear without intervention and can spread.
When to Seek Professional Advice
Seek professional medical advice if a black toenail exhibits certain characteristics or symptoms. Persistent pain, throbbing, or increasing pressure under the nail, especially after an injury, may indicate a subungual hematoma requiring drainage. Signs of infection, such as redness, swelling, warmth, or pus around the nail, also necessitate immediate medical attention. These symptoms could indicate a bacterial infection.
Furthermore, if the black discoloration appears without any known injury or trauma, or if it changes in size, shape, or color, professional assessment is crucial. This is particularly important if the dark streak extends to the cuticle or surrounding skin, as this could be a sign of subungual melanoma. Similarly, if the black area does not appear to grow out with the nail over several months, or if multiple nails are affected without a clear traumatic cause, a medical consultation can help determine the underlying reason and guide appropriate management.
Tips for Care and Prevention
As a black toenail heals, simple care practices can help manage discomfort and prevent complications. Keeping the affected toe clean and dry helps prevent secondary infections. Wearing comfortable, well-fitting shoes that do not press against the toenail avoids further irritation. If the nail is loose or partially detached, careful trimming can prevent snagging, but seek professional help for significant detachment.
Preventing black toenails involves selecting appropriate footwear and practicing good foot hygiene. Ensuring shoes fit properly, with ample room in the toe box, reduces pressure and friction on the nails during daily activities or exercise. Trimming toenails straight across and not too short helps prevent ingrown nails and reduces the nail hitting the front of the shoe. For athletes, wearing properly cushioned athletic shoes and ensuring laces are tied securely minimizes repetitive impact on the toes.