Subungual hematoma is the medical term for bleeding and bruising under the nail. This is usually the result of some kind of injury to the blood vessels under the nail bed. For example, blood vessels can break and leak blood into the area underneath the nail when a door slams on a finger or a heavy object crushes a toe.

A subungual hematoma can also result when toes are repeatedly jammed into the toe box of a too-tight shoe. This is especially true when the person wearing the ill-fitting shoe engages in sports with a lot of stop-and-start action, as in tennis, soccer, or basketball. It can also happen to runners and hikers, especially those who often run or hike downhill.

When space is tight in the front of a shoe, there is undue pressure on the blood vessels in the toes. This can cause the blood vessels to break and bleed under the nail. For these reasons, the condition is also sometimes called runner’s toe or tennis toe.

According to the American Osteopathic College of Dermatology (AOCD), the first symptom of a subungual hematoma is a throbbing pain in the nail area, thanks to the pressure of blood pooling under the nail bed.

The second symptom is the discoloration of the nail. What starts out as a reddish purple will eventually turn dark brown and black as the blood clots. Nail discoloration can be a symptom of other conditions as well.

With a subungual hematoma, the pain typically goes away in a few days. The nail itself will take longer to recover.

The discolored nail will eventually grow out — or in some cases it may fall off or need to be removed — and be replaced by a new, healthy one. This could take anywhere from about eight weeks for a fingernail to six months for a toenail.

A doctor can often diagnose a subungual hematoma based on visual inspection of the nail and any recent trauma you report. For example, if you have symptoms and you recently whacked your finger with a hammer, your doctor will likely diagnose subungual hematoma.

Your doctor may also X-ray the finger or toe to see if there is any fracture associated with the injury.

Melanoma is a serious form of skin cancer that can cause skin — including the skin under the nails — to discolor and sometimes bleed. Melanoma in the nail bed is rare, occurring in just about 1 in 1 million people. But it tends to get diagnosed later and therefore is more likely to be deadly.

To distinguish whether your nail discoloration and bleeding are due to a subungual hematoma or melanoma, your doctor will primarily focus on whether you’ve had a recent injury to your nail or you engage in a sport like running or tennis. Pooling of blood in the nail bed usually occurs within a day or two of a crushing injury and, unlike melanoma, will gradually clear as the nail heals.

As the nail heals from a subungual hematoma, it grows a transverse groove across its surface. Your doctor will look for these and other signs in determining the cause of blood in your nail bed.

Many subungual hematomas can be cared for at home. To reduce swelling, the AOCD recommends elevating the affected foot or hand and icing the area for about 20 minutes at a time. To do this, wrap ice in a cloth or towel or create your own cold compress. Directly applying ice to skin can cause damage. Over-the-counter (OTC) pain medications can also relieve discomfort, and some will also reduce inflammation.

You may need medical treatment if your symptoms are intense or they persist beyond a couple of days. To relieve pressure and pain, your doctor may perform something called nail trephination. This is typically a painless procedure in which a small hole is made in the nail where the blood is pooled, allowing it to drain. Your doctor may do this with a sterile needle or even a sterilized paper clip (this requires skill and shouldn’t be attempted at home). A laser may also be used.

Once the pressure is relieved, most people get immediate relief. The damaged nail will most likely fall off on its own if it isn’t removed by your doctor, which may happen if it’s badly damaged.

Whether your nail is drained or not, it’s important to watch for signs of infection. If you notice any of the following, seek immediate medical attention:

  • a fever
  • the nail feeling warm to the touch
  • red streaks
  • pus draining from the nail

Some subungual hematomas — like those that occur when you smash a finger in a door — are just unfortunate accidents and thus hard to prevent. But others, especially those that involve the toes, are easier to avoid. Some overall recommendations:

In most cases, a subungual hematoma looks worse than it is. Your nail may throb and turn various shades of blue, purple, and brown. It may even fall off. But you can often manage a subungual hematoma with self-care and OTC pain relievers.

If the pain is unrelenting, you can have a simple procedure to drain the blood and relieve pressure underneath the nail. The procedure needs to be done by a skilled medical professional and — regardless if the blood is drained or not —monitored for signs of infection. Once a new nail replaces the old, there’s no need for further treatment or any kind of medical follow-up.