An injury to a fingernail or toenail can cause blood to pool visibly under a nail. This is known as a subungual hematoma.
A subungual hematoma occurs when an injury breaks open blood vessels under the nail, causing blood to collect and become trapped in one spot.
Poorly fitting shoes can also cause subungal hematomas, especially if the person is very active. Shoes that are too tight or narrow can put pressure on the toenail, breaking blood vessels and leading to a pool of blood under the nail.
Running or hiking down steep hills or stopping and starting suddenly, such as while playing soccer or basketball, can also cause a type of subungual hematoma. This is often called runner’s toe.
If a subungual hematoma is small and the pain is mild, it will usually resolve without treatment or complications.
However, if there is severe damage to the nail bed, or if the pain is unmanageable, a person should seek medical treatment.
A person may have a subungual hematoma if they have injured their finger or toe and:
- there appears to be blood under the nail
- the nail feels sore or tender
- it feels like there is pressure under the nail
- the nail is discolored
People with artificial nails may not be able to see a subungual hematoma. If a person feels intense pain and pressure, they should remove the artificial nail and examine the nail bed.
A minor subungual hematoma does not cause serious health problems. Home remedies can help to manage pain while the injury heals.
Over-the-counter pain relievers can reduce discomfort and swelling. In addition, the RICE method can be useful for minor subungual hematomas. RICE stands for:
- Rest: Limit use of the affected finger or toe.
- Ice: Use an ice pack, to reduce swelling and pain.
- Compression: Apply pressure such as a wrap to the area immediately, to reduce the amount of blood that can pool.
- Elevation: Keep the affected hand or foot elevated, to reduce swelling.
For more serious injuries, this may not be enough. Any significant injury to the nail can damage or break the bone underneath. A person should seek medical attention if:
- the pain is unbearable
- the injury happened to a baby or child
- the bleeding is uncontrollable
- there is a cut or laceration
- the base of the nail is damaged
- without injury, any nail turns dark or discolored
A doctor may need to remove a severely injured nail or use stitches for deep cuts.
Sometimes the damaged nail is not removed but used as a cover to protect the nail bed while it heals. The damaged nail may need to be removed at a later date.
When the damaged nail bed heals, the bleeding will stop and a new nail will grow.
If a doctor suspects that the bone is broken, they may order an X-ray. Broken fingertips may be covered with a hard splint for several weeks to promote healing and to protect the area from further injury.
A doctor may perform a procedure called nail trephination to drain the blood from under the nail. This can help to relieve pain and pressure.
The doctor will make a small hole in the nail with a laser or needle. Afterward, the area may be wrapped with a bandage and may continue to drain for up to 3 days.
This procedure should not be attempted at home, as it can cause infections or further injury to the nail bed.
Possible signs of an infection include:
- fluid or pus draining from under the nail
- increased swelling or pain
- red streaks in the skin
- a fever
- a feeling of heat or throbbing in the finger or toe
- excessive redness around the area of injury
If any of these symptoms appear, see a doctor right away.
A tumor may look like a subungual hematoma. Melanoma can cause a dark mark to form under the nail. However, it does not usually cause pain and is not linked to an injury.
Speak to a doctor about any unusual marks or colors on the nail that appear without an injury.
A minor subungual hematoma usually heals over time without treatment. The trapped blood will eventually be reabsorbed, and the dark mark will disappear.
This can take 2–3 months for a fingernail, and up to 9 months for a toenail.
If there is severe damage to the nail bed, the nail may be malformed or cracked when it grows back. Or, it may fail to regrow. This is uncommon, however, and may be prevented by seeing a doctor for treatment when an injury occurs.