Black toenails, though concerning, are a common issue with various underlying causes. Understanding these reasons can help determine the appropriate course of action, from home care to professional medical attention.
Physical Injury and Discoloration
One frequent reason for a toenail to turn black is physical trauma, leading to a subungual hematoma. This occurs when blood vessels beneath the nail rupture, causing blood to pool under the nail plate. Common incidents include dropping a heavy object on the toe, stubbing it forcefully, or repetitive friction from ill-fitting footwear during activities like running or hiking.
The trapped blood initially appears as a dark red or purple spot, deepening to dark brown or black as it coagulates. This accumulation creates pressure, often resulting in throbbing pain. The discoloration will gradually grow out with the nail over several months as new, healthy nail replaces the injured section.
Fungal and Bacterial Infections
Onychomycosis, a fungal infection, is another frequent cause of toenail discoloration, though it typically presents with yellow or brown hues. These infections thrive in warm, moist environments, making feet susceptible. Fungi can cause the nail to thicken, become brittle, and sometimes crumble.
While often yellow or brown, the nail can appear darker due to accumulated debris or a secondary bacterial infection. Bacterial infections, less common as a primary cause of black discoloration, can occur secondary to a fungal infection or trauma, leading to pus and further changes in nail color and texture. Other symptoms may include an unpleasant odor or itching around the affected nail.
Medical Conditions and Medications
Less common but potentially more serious causes for black toenails include certain medical conditions and medication side effects. Conditions like diabetes, kidney disease, or heart conditions can affect nail health, sometimes leading to discoloration or changes in nail structure. Some medications, including chemotherapy drugs, antimalarials, and certain antibiotics, can cause nail discoloration as a side effect.
Subungual melanoma, a rare skin cancer under the nail, is a more serious cause. This condition often presents as a dark, irregular streak that may spread to the cuticle or surrounding skin, and it typically does not have a history of trauma. Unlike a bruise that grows out with the nail, melanoma tends to persist and may even widen or darken over time. Early detection is important for effective treatment.
When to Consult a Doctor
Consult a healthcare professional if toenail discoloration appears without an obvious injury. Persistent or worsening discoloration, especially with pain, swelling, or pus, warrants medical evaluation. Signs of infection, such as redness or warmth around the nail, also require professional assessment.
Seek medical advice if the discoloration spreads to the surrounding skin, or if the nail’s shape or thickness changes significantly. A dark streak under the nail that appeared suddenly, is widening, or extends to the cuticle should be promptly evaluated for melanoma. Individuals with underlying health conditions like diabetes or circulatory issues should also consult a doctor for any nail changes.
Preventing Toenail Discoloration
Preventing toenail discoloration involves adopting simple foot care habits. Wearing properly fitting footwear is important, as shoes that are too tight or narrow can cause repetitive trauma to the toenails during daily activities or exercise. Ensuring shoes have enough space in the toe box can help prevent pressure on the nails.
Keeping toenails clean and dry helps prevent fungal and bacterial growth. Trimming nails correctly, straight across and not too short, reduces the risk of ingrown nails and trauma. Protecting feet in public, moist environments like showers or swimming pools by wearing sandals can significantly reduce exposure to fungi. Regularly inspecting toenails for any changes in color, texture, or shape allows for early detection of potential issues.