A subungual hematoma is the medical term for a common injury where blood pools beneath a fingernail or toenail. This collection of blood usually results from acute trauma, such as a crushing blow or a severe stubbing accident. Because the blood is trapped in a confined space, it creates pressure that causes significant discomfort. When this injury occurs, people often consider professional drainage, but many allow the injury to resolve naturally.
Identifying a Subungual Hematoma
A subungual hematoma is typically triggered by a sudden, forceful event, such as dropping a heavy object onto a digit or slamming a finger in a door frame. Repetitive trauma, like pressure from ill-fitting athletic shoes during long-distance running, can also cause this injury. The immediate result is the rupture of small blood vessels in the nail bed, leading to bleeding.
The most noticeable symptom is a dark discoloration beneath the nail, which can appear red, purple, dark brown, or black, depending on the age and volume of the trapped blood. The accumulation of blood under the rigid nail plate creates intense pressure against the sensitive nail bed tissue. This pressure manifests as severe, throbbing pain that often feels worse than the initial injury itself. This pain provides a strong indication of the hematoma’s size and severity.
The Immediate Goal of Drainage
When a subungual hematoma causes intense pain, a procedure known as trephination is often performed for immediate relief. This intervention involves creating a small hole through the nail plate directly over the blood collection. The purpose is to release the built-up pressure from the trapped blood, which instantly alleviates the throbbing sensation.
This pressure-relief procedure is most effective when performed shortly after the injury, typically within 48 hours. After this timeframe, the accumulated blood often clots and solidifies, making it difficult to drain effectively. For smaller hematomas covering less than a quarter of the nail area, drainage is often unnecessary. In these cases, the pressure naturally subsides within a few days.
The Natural Healing Process Without Intervention
Choosing not to drain a small or moderate subungual hematoma allows the body to manage the blood collection naturally. Once the initial pressure pain subsides, the pooled blood beneath the nail forms a solid, dried clot. This clot cannot be reabsorbed because it is trapped and separated from the underlying tissue by the nail bed.
The dark discoloration remains fixed to the nail bed tissue. The only way for the visible hematoma to resolve is for the nail plate to grow out completely. As the new, healthy nail is generated from the matrix at the base, it slowly pushes the damaged, discolored section forward.
This process requires considerable patience, as nail growth is slow and steady. A fingernail may take six to nine months to fully replace itself. A toenail can take significantly longer, often requiring 12 to 18 months for the discoloration to reach the tip and be trimmed away. For most subungual hematomas without underlying structural damage, this non-intervention approach results in a successful, though slow, resolution.
Potential Complications Requiring Further Treatment
While most undrained hematomas heal well, certain underlying injuries or subsequent issues necessitate medical attention. The collection of blood under the nail, especially if the skin barrier is broken, can create an environment susceptible to bacterial growth. Signs of infection, such as increasing redness, swelling, pus drainage, or warmth days after the injury, require professional treatment.
The force that caused the hematoma may have also damaged deeper structures. A severe crush injury can result in a laceration to the nail bed itself or a fracture of the distal phalanx, which is the bone at the fingertip. In these cases, the nail plate must often be removed by a clinician to allow for surgical repair or to treat the bone fracture. Leaving these severe injuries untreated can lead to nail dystrophy, where the new nail grows back permanently deformed due to damage to the nail matrix.