Everyday Reasons for Black Toenails
A black toenail often results from direct physical trauma, known as a subungual hematoma. This happens when blood vessels beneath the nail plate rupture, causing blood to pool. This can be caused by dropping a heavy object on the toe, stubbing it, or from repetitive micro-trauma. The pressure from the accumulated blood can cause discomfort and discoloration, ranging from dark red to black.
Ill-fitting footwear, particularly shoes that are too tight or too loose, can also cause this type of trauma. Activities like running, hiking, or sports involving sudden stops and starts can lead to the toe repeatedly hitting the front of the shoe. This constant impact can injure the nail bed. Over time, the discolored nail may lift from the nail bed or eventually fall off as a new, healthy nail grows underneath.
Fungal infections (onychomycosis) can also cause toenail discoloration. While often starting as white or yellow spots, these infections can progress, causing the nail to thicken, become brittle, or crumble. As the infection deepens, debris can accumulate under the nail, and the nail itself can darken, sometimes appearing brown or black, potentially due to secondary bacterial infections or fungal pigments.
Other Potential Explanations
Certain serious conditions can also cause toenail discoloration, including melanoma. Subungual melanoma is a rare but aggressive form of skin cancer that develops under the nail. It often appears as a dark, irregular streak or band that extends from the nail bed to the tip of the nail. Unlike a bruise, this discoloration typically does not grow out with the nail and may widen over time. This type of melanoma might also cause the nail to lift from the nail bed, bleed, or lead to a nodule forming under the nail.
Some medications can also lead to nail discoloration as a side effect. Certain chemotherapy drugs, antimalarials, and even some antibiotics can cause the nails to darken or develop stripes. These changes usually resolve once the medication is stopped. Systemic diseases, such as kidney disease, Addison’s disease, or certain autoimmune disorders, may also manifest with nail changes, including discoloration.
When Professional Help is Needed
Professional medical help is needed for any persistent or concerning toenail changes. Consult a doctor if a black toenail develops without clear trauma, or if the discoloration does not grow out with the nail. Severe pain, throbbing, or signs of infection such as redness, swelling, pus, or warmth around the nail also indicate a need for medical attention.
Changes in nail shape or texture, or if the nail begins to separate from the nail bed, should also prompt a visit to a healthcare provider. If you suspect a fungal infection not improving with general hygiene or over-the-counter remedies, a diagnosis can guide appropriate treatment. Any dark streak under the nail that appears new, is growing, or involves the surrounding skin, requires immediate evaluation to rule out serious conditions like melanoma. Only a medical professional can accurately diagnose the cause and recommend effective action.
Caring for Your Toenails
Preventative measures can significantly reduce the likelihood of developing black toenails. Wearing properly fitting shoes, ensuring enough room in the toe box, prevents repetitive trauma during activity. Protecting your feet with appropriate footwear, such as steel-toed boots in hazardous environments, can also prevent direct impact injuries. Regularly trimming toenails straight across and not too short helps prevent ingrown nails and reduces pressure.
Maintaining good foot hygiene is also important. This includes washing feet regularly, drying them thoroughly, especially between the toes, and wearing clean, breathable socks. These practices help create an environment less conducive to fungal growth. For existing discoloration, avoid attempting to self-treat with home remedies. Keep the area clean and dry, and observe for any changes while awaiting professional advice.