A black dot on a toenail often prompts concern. While this discoloration is common and often benign, understanding its various causes can help determine if medical attention is necessary.
Understanding Common Causes
A frequent reason for a black dot on a toenail is a subungual hematoma, a bruise under the nail. This occurs when blood vessels beneath the nail rupture, causing blood to pool. Trauma, such as dropping a heavy object or repeated pressure from ill-fitting shoes during activities like running, can cause this. The trapped blood can appear reddish-brown, purple, or black, and may cause pain or throbbing. A subungual hematoma usually resolves as the nail grows out, with the discoloration eventually disappearing.
Fungal infections, known as onychomycosis, can also lead to dark spots or discoloration on toenails. These infections thrive in warm, moist environments and can cause the nail to change color, often appearing white, yellow, brown, or black. The nail may also thicken, become brittle, or lift from the nail bed. While less common than trauma, certain fungal types can specifically present as black spots.
Benign melanonychia refers to a dark streak or band running lengthwise on the nail. This condition results from increased pigment production by melanocytes, the cells that produce color in the skin and nails. While often harmless, these streaks can sometimes resemble subungual melanoma, a serious form of skin cancer. Less commonly, certain medications or underlying health conditions like diabetes can also lead to toenail discoloration.
Recognizing Warning Signs
While many black spots are harmless, certain characteristics signal a need for medical evaluation to rule out serious conditions like subungual melanoma. Subungual melanoma is a rare skin cancer that develops under the nail, often appearing as a brown or black streak. Unlike a bruise, a melanoma streak typically does not heal or move outward with nail growth, though it may enlarge.
A significant warning sign is a dark streak that extends from the nail plate onto the surrounding skin or cuticle, known as Hutchinson’s sign. Other concerning indicators include changes in the size, shape, or color of the spot, particularly if it grows larger or becomes irregularly shaped. Bleeding, ulceration, or a nodule beneath or around the nail also warrant immediate attention. If a black dot appears without clear history of injury or trauma, or if there is persistent pain, swelling, or the nail separates from the nail bed, it is advisable to seek medical advice. Early detection of subungual melanoma is important for effective treatment.
Medical Evaluation and Management
When a black dot on a toenail prompts concern, a medical professional will typically begin with a visual examination and a detailed medical history, inquiring about any recent injuries or changes. A dermatoscope, a specialized magnifying tool, may be used to gain a clearer view of the nail bed and assess pigment patterns. If a fungal infection is suspected, a nail clipping may be taken for a fungal culture or microscopic examination.
If subungual melanoma is a possibility, a biopsy of the nail matrix and nail bed is often performed to examine cells for cancerous changes. Imaging, such as X-rays, might be used if a bone fracture or other injury is suspected, particularly with trauma-induced discoloration. Once diagnosed, management varies.
For a subungual hematoma causing significant pain, a procedure called trephination may be performed to drain the pooled blood, relieving pressure. Fungal infections are commonly treated with topical antifungal medications; oral drugs may be prescribed for more extensive or persistent cases. For subungual melanoma, surgical removal of the affected area, which may include the entire nail or a portion of the digit, is the primary treatment. Additional therapies like radiation or chemotherapy may be recommended if the cancer has spread.
Maintaining Toenail Health
Maintaining good toenail health can help prevent some common causes of black dots, particularly those related to trauma and fungal infections. Proper footwear plays a significant role; shoes that fit well and have a wide toe box reduce pressure on the nails, minimizing the risk of subungual hematomas from repetitive impact. Breathable materials in shoes also help keep feet dry, preventing fungal growth.
Appropriate nail trimming techniques are also beneficial. Toenails should be cut straight across, not too short, and without curving the corners, to prevent ingrown nails and associated trauma. Regular hygiene practices, such as washing feet daily with soap and water and thoroughly drying them, especially between the toes, reduce the moist conditions fungi favor. Wearing protective footwear in public areas like pools and locker rooms can also help avoid exposure to fungal spores.