A black discoloration beneath a toenail, medically known as subungual discoloration, is a common concern. This change in color is a symptom, indicating that something has affected the nail bed or plate. Understanding the underlying cause is paramount, as the correct approach to eliminating the discoloration depends entirely on what created it. Getting rid of the black area involves allowing the nail to grow out naturally, treating an infection, or addressing a medical issue.
Identifying the Cause
The majority of black toenails result from physical trauma, leading to a subungual hematoma. This occurs when blood vessels beneath the nail bed rupture, causing blood to pool between the nail plate and the underlying tissue. The resulting discoloration is typically dark red, purple, or black, often correlating with a recent injury, such as dropping an object on the toe or repetitive impact from ill-fitting shoes during activities like running.
Another possible cause is a fungal infection, such as onychomycosis or tinea unguium, which develops beneath the nail. While fungal infections commonly cause yellow or white discoloration, a dark brown or black appearance can result from debris buildup or secondary bacterial infections. Fungal discoloration often begins at the edge of the nail and is accompanied by thickening, crumbling, or a distorted nail shape.
A much rarer, but more concerning, cause is subungual melanoma, a form of skin cancer that develops in the nail matrix. Red flags include a dark, pigmented streak that runs vertically from the cuticle to the tip of the nail and does not grow out. A strong indicator is the discoloration spreading to the skin surrounding the nail, known as Hutchinson’s sign. Unlike a hematoma, melanoma typically appears without a history of trauma and may change in size or shape over time.
Immediate Steps for Minor Trauma
If the black spot is the result of a minor, recent injury and does not involve severe pain or large discoloration, home management focuses on reducing swelling and discomfort. The R.I.C.E. protocol (Rest, Ice, Compression, and Elevation) should be applied immediately after the trauma. Resting the foot and applying a cold pack for 10 to 20 minutes can help minimize swelling and pain.
Elevating the foot above heart level helps slow blood flow to the area, limiting the amount of bleeding and pooling under the nail. For a small hematoma, the trapped blood will eventually be reabsorbed by the body, and the discoloration will simply grow out with the nail. Since toenails grow slowly, this can take six to twelve months, and there is no method to speed up the process.
Avoid the temptation to drain the blood yourself using household items like a heated paperclip or needle. Attempting to puncture the nail at home significantly increases the risk of introducing bacteria, leading to a serious infection of the nail bed or surrounding tissue. A medical professional should always perform any drainage procedure in a sterile environment.
When Medical Treatment is Necessary
Professional medical intervention is necessary when a subungual hematoma causes intense throbbing pain due to pressure buildup, or when the underlying cause is not trauma. For large, painful hematomas, a procedure called trephination is performed to relieve the pressure. A healthcare provider creates a small hole in the nail plate using a sterile instrument, such as an electrocautery device or a specialized needle.
This small opening allows the pooled blood to drain, instantly relieving the pressure and associated pain. This technique does not immediately remove the black coloration but prevents potential long-term damage to the nail bed and speeds up symptom resolution. Trephination is most effective when performed within 48 hours of the injury, before the blood has fully clotted.
If a fungal infection is suspected, a medical professional will take a small clipping or scraping of the nail for laboratory culture and diagnosis. Treatment for tinea unguium often involves prescription oral antifungal medications, such as terbinafine or itraconazole, which are more effective than topical treatments. These medications are typically taken for several weeks or months, as successful treatment requires the entire infected nail to be replaced by new, clear growth.
If the discoloration presents with features concerning for melanoma, a biopsy of the affected nail bed tissue is the only way to confirm a diagnosis. If melanoma is confirmed, treatment involves surgical excision to remove the cancerous tissue. In severe cases where the cancer has progressed, a wider surgical margin or even amputation of the toe tip may be necessary to ensure complete removal.
Preventing Toenail Discoloration
Preventing black toenails involves minimizing the trauma and moisture that facilitate the two most common causes. Proper shoe fit is a primary preventative measure, especially for individuals who engage in activities like running or hiking. Ensure there is approximately a half-inch of space, or a thumb’s width, between the longest toe and the end of the shoe to prevent repeated jamming against the toe box.
Maintaining good foot hygiene is an effective preventative strategy against fungal infections. This includes wearing moisture-wicking socks to keep the feet dry, as fungi thrive in warm, damp environments. Toenails should be trimmed regularly and straight across to prevent them from rubbing against the shoe or becoming ingrown, which can create entry points for infection.
Avoid walking barefoot in public, moist areas like locker rooms, communal showers, and swimming pool decks to reduce exposure to fungal organisms. When purchasing new athletic shoes, consider having your feet professionally measured later in the day, as feet often swell, ensuring the best fit.