When blood becomes trapped under the toenail a condition exists called subungual hematoma.
Symptoms are dark red coloring under the nail plate, usually following some injury or traumatic event. The color may change or remain the same for a long time ranging from red, dark red, brown, or even black. This may or may not cause pain or swelling. If this dark colored appearance of your nail is seen without recalling any trauma, you should have this thoroughly evaluated by your podiatrist as other more serious conditions such as cancerous lesions can occur under the nail.
Causes of subungual hematoma are trauma related, either a direct impact like something dropped on your toe, or from repetitive trauma as an old tight shoe may trigger.
Prevention of subungual hematoma is to avoid the traumatic event, which most are unavoidable. If the injury occurs due to shoewear being too tight against the toe, new shoes or modifications may prevent the hematoma. People taking any type of blood thinning medications like non-steroidal anti-inflammatories are more prone to the hematoma with injury. When injury first occurs to the nail, ice may relieve some of the pain and swelling. You should also avoid putting weight on this part of your foot until evaluated as there may also be an associated foot fracture.
Podiatric Care may include doing nothing except observing the injury as it “grows out”. The nail may continue to grow and the hematoma resolve on its own depending on the severity of injury. The nail may also fall off over this period of time as the nail has become loosened from the nail bed. When this occurs the nail usually grows back in time, but occasionally the trauma also injured the nail matrix causing permanent nail growth deformities. If the injury is severe enough, your podiatrist may decide the best treatment is to remove the nail entirely, or force a hole in the nail to drain the blood from underneath. A nail can become infected with a large pocket of dried blood. Relieving the blood from beneath the nail may also remove the pressure relieving the pain.