A subungual hematoma is a pool of blood that builds up underneath a finger or toenail. It is a common result of a traumatic nail bed injury, which can occur if a digit is smashed in a door, stepped on, or otherwise crushed under pressure. Blood vessels underneath the nail break and leak blood into the nail bed, leading to a buildup of pressure and often intense pain. In most cases, a small subungual hematoma will go away on its own in about two weeks without special care. A very large or painful hematoma can be relieved at a doctor's office by draining the blood or removing the damaged nail.
Trauma to a nail that compresses it down into the nail bed causes delicate blood vessels to rupture. The leaking blood collects underneath the nail and forms a dark red or purple spot. Accumulating pressure can cause a finger or toe to throb and feel very tender to the touch. Depending on the severity of the injury, a person may experience constant pain, weakness, and swelling in addition to a subungual hematoma.
Home remedies are usually enough to relieve symptoms while a mild hematoma heals. A person can reduce throbbing and pain by keeping the digit elevated and applying an ice pack several times a day. It is important to rest the finger or toe as much as possible in the first few days to avoid further irritation. Over-the-counter anti-inflammatory drugs such as aspirin and ibuprofen also may help to relieve pain. As the nail heals, the dark spot gradually becomes smaller and lighter in color until it is completely gone.
A person should visit a doctor if he or she experiences severe pain and the subungual hematoma takes up most of the space underneath the nail. The physician can carefully examine the digit to check for lacerations to the underlying nail bed. X-rays may be taken if a bone fracture is suspected because of the degree of swelling and pain.
An experienced doctor can drain a subungual hematoma by piercing the nail with the tip of a heated needle or paper clip. Once a small hole is created, pressure is instantly relieved as blood drains from the nail bed. The entire nail may need to be removed if the physician thinks the nail bed may be seriously damaged. The exposed bed is treated with antibiotics and wrapped in a protective bandage to prevent infection. The digit is usually tender for several days, but it eventually starts feeling better as swelling subsides and a new nail starts growing into place.