A black toe refers to a discoloration of the toenail, often appearing black, dark blue, or purple. This change in color indicates an issue beneath the nail plate, such as bleeding or pigment changes. While common, a black toenail is frequently a benign condition.
Primary Causes of Black Toe
The most common reason for a black toenail is a subungual hematoma, which is blood pooling under the toenail. This occurs due to trauma or injury to the nail bed, causing discoloration as blood collects.
Acute trauma, such as stubbing a toe, dropping a heavy object, or kicking something hard, can directly cause a subungual hematoma. The impact damages small blood vessels beneath the nail, leading to bleeding and subsequent discoloration. This injury can cause significant pain due to pressure from the trapped blood.
Repetitive microtrauma is another frequent cause, especially in activities like running, hiking, or wearing ill-fitting shoes. Constant pressure or friction on the toenail, often from shoes that are too tight or too loose, can injure the nail bed over time. This repeated stress causes minor bleeding that accumulates, eventually resulting in a black or darkened appearance.
Other Underlying Conditions
While trauma is a common cause, other medical conditions can also lead to toenail discoloration. Fungal infections (onychomycosis) can sometimes cause the nail to darken, though they often appear yellow or brown. Fungi thrive in warm, moist environments and can cause the nail to thicken, become brittle, or even separate from the nail bed.
Subungual melanoma is a rare but serious type of skin cancer that develops under the nail. It may appear as a dark brown or black streak, often running vertically. Unlike a bruise, this discoloration typically does not grow out with the nail and may change in size or appearance, sometimes extending to the surrounding skin.
Severe cold exposure, leading to frostbite, can also cause discoloration of the toe, including the nail. Frostbite results from the freezing of skin and underlying tissues, which can lead to tissue damage and a change in skin color to blue or black in advanced stages.
When to Seek Medical Attention
Seek medical attention for a black toe under several circumstances. Persistent or severe pain, increasing swelling, warmth, or pus around the nail can indicate an infection. Discoloration that spreads, does not improve, or appears without obvious trauma warrants evaluation.
If there is any suspicion of melanoma, such as a dark streak that changes, has irregular borders, or involves the surrounding skin, seek prompt medical advice. A healthcare provider can diagnose the cause and recommend appropriate action. If you suspect a fracture due to severe trauma, especially if you cannot bear weight on the toe, a doctor’s visit is necessary.
For minor subungual hematoma cases where pain is manageable and there are no signs of infection, self-care like rest and cold compresses might be sufficient. However, if discoloration covers more than half the nail, or if intense throbbing pain persists, a doctor may need to drain the blood to relieve pressure. Draining a subungual hematoma should only be performed by a healthcare professional.