Common Causes of Black Toenails
Black discoloration of a toenail can be alarming. While the causes range from relatively harmless incidents to more serious underlying conditions, understanding them helps determine the appropriate course of action.
A frequent cause is a subungual hematoma, a bruise beneath the nail plate. This typically results from trauma, such as dropping an object, stubbing a toe, or wearing tight shoes. Repetitive stress from activities like running or hiking can also rupture blood vessels under the nail. As blood accumulates, it becomes trapped and appears dark. This discoloration gradually resolves as the nail grows out.
Another common reason is a fungal infection. Fungi can invade the nail, leading to dark discoloration. Fungal infections often present with additional symptoms beyond color change. The infected nail might become thickened, brittle, or crumbly, and may lift away from the nail bed. Risk factors include wearing occlusive footwear, excessive sweating, and walking barefoot in warm, moist environments like public showers.
Less Common, More Serious Causes
Several serious conditions can also cause a black toenail. One concern is subungual melanoma, a rare form of skin cancer that develops under the nail. This often manifests as a dark streak or patch originating at the cuticle and extending towards the nail tip. Unlike a bruise, melanoma discoloration does not grow out or resolve. Early detection is important for successful treatment.
Certain medications can also lead to nail discoloration as a side effect. Drugs like some chemotherapy agents, antimalarial medications, and the antibiotic minocycline can cause changes in nail pigmentation. The discoloration can appear as dark bands or a generalized darkening. These changes are benign and usually resolve after the medication is discontinued.
Underlying health conditions can also contribute to nail changes, including discoloration. Systemic diseases like diabetes, kidney disease, or heart conditions affect circulation and overall nail health. Poor blood flow to the extremities can lead to nail bed changes and discoloration. These instances are often accompanied by other symptoms related to the primary health condition.
When to See a Doctor
Consult a doctor if a black toenail develops without a clear injury. Seek prompt medical attention if the discoloration is accompanied by pain, swelling, or pus around the nail. These symptoms could indicate an infection or a more serious underlying issue.
See a doctor if the black area appears to be spreading or changing rapidly in size or intensity. Also, seek evaluation if the discoloration presents as a dark stripe originating from the cuticle and extending to the nail tip, especially if it involves the skin under the nail.
If multiple toenails are affected without an obvious cause, or if the discoloration does not improve or resolve as the nail grows out, consult a doctor. Individuals with chronic health conditions, such as diabetes, should monitor any changes in their feet or toenails, as these conditions can increase complication risk.
Preventing Black Toenails
Preventing black toenails involves proper foot care and protection. Wearing correctly fitting footwear is a primary preventive step. Shoes should have ample toe room, preventing compression or rubbing, especially during activities like running or hiking. Properly fitting shoes significantly reduce the risk of repetitive trauma to the toenails.
Regular nail care also helps prevent black toenails. Trim toenails straight across and not too short to prevent ingrown nails and reduce pressure from footwear. Maintain good foot hygiene by keeping feet clean and dry to prevent fungal infections, a common cause of nail discoloration. Wearing breathable socks and changing them regularly also promotes foot health.