What are the causes of black toenail?

Black toenails, also known as subungual hematoma, can be caused by various factors, including:

1. Trauma: Stubbing your toe, dropping a heavy object on it, or wearing ill-fitting shoes that repeatedly press against the toenail can cause blood vessels underneath the nail to rupture, leading to bleeding and the formation of a black spot or discoloration.
2. Repetitive Stress: Activities that involve repetitive impact or pressure on the toes, such as running, hiking, or playing sports, can increase the risk of developing black toenails due to repetitive trauma to the nail bed.
3. Tight Shoes: Wearing shoes that are too tight or narrow can squeeze the toes and put pressure on the toenails, leading to friction, irritation, and potential injury to the nail bed.
4. Fungal Infection: In some cases, a fungal infection of the toenail, known as onychomycosis, can cause discoloration, thickening, and blackening of the nail. Fungal infections often develop gradually over time and may be accompanied by other symptoms such as thickening, brittleness, or a foul odor.
5. Bacterial Infection: In rare cases, a bacterial infection around the toenail, such as paronychia, can lead to inflammation, swelling, and discoloration of the nail bed, including the development of black spots or lines.
6. Blood Disorders: Certain underlying medical conditions or blood disorders, such as clotting disorders or vascular abnormalities, can increase the risk of spontaneous bleeding or bruising under the toenails, leading to the formation of black toenails.
7. Medications: Some medications, such as anticoagulants (blood thinners) or chemotherapy drugs, can increase the risk of bleeding or bruising, which may manifest as black toenails in some individuals.

If you have a black toenail and are unsure of the cause or if it's associated with pain, swelling, or signs of infection, it's essential to consult with a healthcare professional for evaluation and appropriate management. They can assess the underlying cause of the black toenail and recommend the most suitable treatment or preventive measures to promote healing and prevent recurrence.