A bruised toenail, medically termed a subungual hematoma, is a common injury resulting from trauma that causes blood to pool beneath the nail plate. This occurs when small blood vessels in the nail bed rupture, leading to an accumulation of blood in the confined space between the nail and the underlying soft tissue. Subungual hematomas are common in both athletes and the general population due to the toes’ vulnerability to impact and repetitive stress. The resulting discoloration and throbbing pain are direct consequences of this internal bleeding and pressure build-up.
Identifying the Visual Signs of a Bruised Toenail
The appearance of a bruised toenail is characterized by discoloration directly beneath the nail plate. Immediately following the injury, the pooled blood typically presents as a red or purplish patch. As the blood clots, the color progresses to darker shades, often turning dark blue, brown, or black over the next few days or weeks.
This discoloration can manifest as a blotchy mark, a thin streak, or cover the entire nail bed, depending on the trauma’s severity and location. A distinguishing characteristic of a subungual hematoma is that the dark spot is fixed; the color does not change when pressure is applied to the nail surface. The trapped blood remains visible until the nail grows out because it is physically locked between the nail and the underlying tissue.
Mechanisms of Injury: How Subungual Hematomas Form
Subungual hematomas form when force is applied to the toenail, causing blood vessels in the nail bed to break. This trauma is categorized into two primary mechanisms: acute trauma and repetitive microtrauma.
Acute Trauma
Acute trauma involves a sudden, severe impact, such as stubbing a toe, dropping a heavy item on the foot, or a crush injury. This typically results in immediate, intense pain due to the rapid pooling of blood and subsequent pressure on the nail bed nerves.
Repetitive Microtrauma
Repetitive microtrauma involves continuous, low-level stress repeated over time. This is common in long-distance runners or hikers whose toes repeatedly strike the front of ill-fitting footwear. This mechanism causes gradual injury to the vessels, meaning discoloration and pain develop more slowly.
Immediate Care and Critical Warning Signs
For a minor bruised toenail, immediate self-care helps manage symptoms and reduce swelling. The R.I.C.E. protocol (Rest, Ice, Compression, and Elevation) is recommended to limit bleeding and swelling in the initial hours following the injury. Applying a cold compress wrapped in a cloth can help numb the area and reduce inflammation. Over-the-counter pain relievers can also alleviate discomfort and throbbing pain.
Professional medical attention is needed if certain warning signs appear. Severe, throbbing pain that does not improve with home care suggests significant pressure from the trapped blood. This pressure may require draining by a healthcare provider in a sterile procedure called trephination. Other signs include infection, such as increasing redness, warmth, pus draining from under the nail, or a fever. Evaluation is also necessary if the bruise covers more than half of the nail surface or if an underlying toe bone fracture is suspected.
The Long-Term Process of Nail Resolution
The discolored section of a bruised toenail must grow out with the nail plate. The resolution of a subungual hematoma depends on the toenail’s natural, slow growth cycle. Since toenails grow at an average rate of about one millimeter per month, the process can take six to twelve months for the entire nail to be replaced.
As the nail grows, the dark patch slowly migrates toward the tip of the toe until it can be trimmed away. If the initial trauma was significant, the pressure from the hematoma may cause the nail to loosen and detach partially or completely from the nail bed, a condition known as onycholysis. If the nail is shed, a new, healthy nail typically grows in its place from the nail matrix.