A black toenail typically indicates changes in the nail plate or underlying tissue, often due to bleeding or pigment alterations. While frequently a benign occurrence, such discoloration can sometimes signal a more serious condition that warrants medical attention. Understanding the various reasons a toenail might turn black is important for identifying when concern is justified.
Understanding the Causes
The most common reason for a toenail to turn black is a subungual hematoma, which is essentially a bruise under the nail. This happens when blood vessels beneath the nail bed rupture, causing blood to pool. Such an injury can result from a single impact, like stubbing a toe or dropping an object on it, or from repeated minor trauma, such as wearing ill-fitting shoes or engaging in activities like running. The trapped blood appears dark, and the discoloration usually resolves as the nail grows out over several months.
Fungal infections, medically known as onychomycosis, can also cause toenail discoloration, sometimes leading to a black appearance. These infections often begin as white or yellow spots, with the nail potentially darkening to brown or black as the fungus progresses and debris accumulates underneath. Fungal infections can also cause the nail to thicken, become brittle, or crumble.
Subungual melanoma, a rare form of skin cancer, can also cause black toenails. It often appears as a dark streak or discoloration, unrelated to injury, that expands over time. Unlike a bruise, a melanoma streak will not grow out with the nail or disappear. Other less common factors include certain medications, benign moles under the nail, or underlying systemic diseases like diabetes or kidney disease.
When to Be Concerned
Certain signs indicate a black toenail may be more than a simple bruise, warranting medical evaluation. Seek professional advice if discoloration appears without known trauma or injury. Also concerning is persistent or worsening pain.
Spreading discoloration, especially if the dark area extends to the cuticle or the surrounding skin (Hutchinson’s sign), suggests melanoma. Changes in the nail’s appearance, such as brittleness, lifting from the nail bed, or unusual ridges without obvious cause, also warrant attention.
If multiple toenails turn black without clear trauma, or if there are signs of infection like redness, swelling, pus, or warmth around the nail, consult a doctor. Any dark streak under the nail that changes in size, shape, or color, or is wider at the cuticle, should be examined for potential subungual melanoma.
Next Steps and Treatment Options
For black toenails caused by trauma, minor cases can often be managed with self-care measures. Applying ice to reduce swelling and pain, and elevating the foot, can provide relief. If significant pressure and pain are present due to a large collection of blood, a medical professional might perform a procedure called trephination. This involves creating a small hole in the nail to drain the trapped blood, which can immediately alleviate pressure and discomfort.
Fungal nail infections typically require antifungal medications. These can be topical solutions applied directly to the nail or oral medications prescribed by a doctor. Oral antifungals may need to be taken for several months, and a healthcare provider might monitor liver function during this period. It is important to complete the full course of treatment to clear the infection.
If subungual melanoma is suspected, a biopsy of the nail matrix and nail bed is necessary for an accurate diagnosis. Treatment for confirmed melanoma usually involves surgical removal of the affected portion of the nail or digit. Early detection is important, as melanoma can spread if left untreated. Maintaining good foot hygiene, trimming nails properly, and wearing well-fitting shoes can help prevent some common causes of black toenails.