What causes unexplained bruising under the big toenail?

Generally, unexplained bruising under the toenail may be caused by hidden external trauma, compression and friction from shoes or socks, thrombocytopenic purpura, subungual glomus tumor, coagulation disorders, or other reasons. It is recommended to seek medical attention promptly, identify the underlying cause, and receive symptomatic treatment under a doctor's guidance. Specific analyses are as follows:

1. Hidden external trauma: Minor bumps or impacts to the toes during daily walking or exercise may go unnoticed at the time, but later lead to rupture of capillaries beneath the nail, resulting in bruising. Avoid further pressure on the toes and wear loose-fitting shoes. During the early stage of bruising, apply an ice pack for cold compression to stop bleeding; after 48 hours, switch to warm compresses with a hot towel to promote absorption of the hematoma.

2. Compression and friction from shoes or socks: Wearing shoes that are too small or tight over a long period can continuously compress the toes, causing blood vessels under the nail to rupture and result in bruising. Immediately switch to well-fitting, breathable footwear, choosing round-toed styles with soft soles. Avoid high heels or pointed shoes to reduce pressure on the toes.

3. Thrombocytopenic purpura: Reduced platelet count leads to impaired clotting function, making skin and mucous membranes prone to bleeding, manifesting as unexplained bruising under the nail. Patients should follow medical advice to take medications such as prednisone tablets, methylprednisolone tablets, or polypeptide-aminophenyl sulfonic acid tablets to increase platelet counts and improve coagulation.

4. Subungual glomus tumor: Abnormal proliferation of blood vessels under the nail forms a tumor, which tends to bleed easily even with slight stimulation, causing nail bruising accompanied by localized pain. Patients should follow medical advice to use ibuprofen sustained-release capsules, acetaminophen tablets, or diclofenac sodium enteric-coated tablets to relieve pain. Surgical excision of the subungual glomus tumor is required to completely remove the lesion.

5. Coagulation disorder: Deficiency or dysfunction of clotting factors reduces blood's ability to clot, leading to spontaneous bleeding under the nail and bruising. Patients should follow medical advice to supplement clotting factors and use medications such as vitamin K1 injection, tranexamic acid tablets, or etamsylate injection to improve coagulation function.

Perform proper warm-up exercises before physical activity to prevent toe injuries during intense exercise. Increase intake of foods rich in vitamin C, such as oranges and kiwifruits, to promote vascular repair. Regularly monitor changes in the bruising; if it recurs frequently or spreads in size, promptly undergo complete blood count and coagulation function tests.