A subungual hematoma is a transient condition where blood and fluid collect underneath the fingernail or toenail. This is usually caused by a traumatic injury as in hitting your thumb with a hammer or stubbing a toe. It can also occur from wearing tight-fitting shoes which trap blood in the toes leading to an increased pressure within the blood vessels of the toes. In either case, the injury leads to the breakage of small blood vessels underneath the nail which leak blood into a potential space below the nail that causes discoloration of the nail and intense pressure.
Initially the injury may only hurt. The nail may feel sore or tender to the touch. As the blood pools under the nail the pressure from the blood can cause severe pain. The pressure caused by blood underneath the nail may result in the affected nail lifting off the finger or toe. The color under the nail will change over time initially red to purple and later to dark brown and black as the blood clots. The pain usually resolves days after the injury and the nail looks worse than it feels.
Usually the treatment is minimal and consists of rest, ice, elevation, and compression of the finger or toe. Over the counter pain medication can be given if needed. Elevation and the use of ice help to reduce the swelling and further pain. Placing ice directly on the affected nail could cause further injury, so wrapping ice in a cloth towel and applying it to the affected area works best. Compression can further reduce the bleeding underneath the nail. Regardless of treatment the hematoma will eventually be resorbed by the body and a new nail will grow out. On average the nail takes 6 to 9 months to grow completely out. A complication to be aware of is damaging the cells that re-grows the nail (the nail matrix). If the nail matrix is damaged the nail will grow incorrectly or may not re-grow a nail.
There are a few reasons to seek medical attention: if bleeding does not stop, if the pain becomes too intense, or if there is significant injury to the base of the nail. Depending on the manner of injury issues to be aware of would be; a deep cut or laceration to the skin of the finger or toe underneath the nail that may require stitches as well as taking an x-ray to determine if the bone of the finger or toe involved is broken. If necessary the pressure caused by the hematoma can be resolved by a medical professional using a technique called trephination. This is done by using a sharp instrument to pierce the nail and drain the blood which relieves the pain. Drainage or removing the nail is discouraged from being attempted by the public because this could lead to further complications of infection, additional trauma, slowing of the healing process, or leaving the finger or toe vulnerable.
Over the course of several months a new nail replaces the damaged, discolored nail. There usually is no need for further treatment or follow up.
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