Nail Trauma: Injured Fingernails and Toenails

How a nail is built

The nail plate is made of hard keratin. Underneath it is the nail bed, a thin, blood-rich layer firmly attached to the bone. The nail grows from the germinal matrix, hidden under the skin fold at the base of the nail (the pale half-moon, or lunula, is its visible edge). Injury to the matrix or nail bed can cause the nail to regrow ridged, split or detached, so these structures are what treatment aims to protect.

Fingernails grow about 3 mm (1/8 inch) a month; toenails grow much more slowly.

Types of nail trauma

Blood under the nail (subungual hematoma)

Crushing a finger in a door or dropping something heavy on a toe ruptures small vessels in the nail bed. Trapped blood builds pressure, causing intense throbbing and a red, purple or black color under the nail.

• Small and mildly painful: leave it alone. The mark grows out with the nail over months.
• Large and very painful, within about 48 hours: a clinician can drain it by making a small hole in the nail (trephination) with a heated wire or fine needle. Relief is often immediate. Do not try this at home with a hot paperclip, which risks burns and infection.
• Large hematoma with a broken nail edge or fracture: the nail bed may need to be checked and repaired.

Black toenail

Repeated pressure from tight or short shoes in running, hiking or soccer causes slow bleeding under the big or second toenail. It is usually painless or mildly sore. The nail often loosens and falls off over weeks as a new one grows.

Nail bed laceration

A cut through the nail bed, often from a saw, knife or crush, usually with a cracked or loose nail. Clinicians may remove the nail, stitch the nail bed with fine dissolvable stitches or tissue glue, and place the nail (or a splint) back in the fold to keep it open while healing. An X-ray checks for a fracture of the fingertip bone, which is common with crush injuries. More severe crush and tip injuries are covered on our fingertip injury page.

Nail avulsion (torn-off nail)

A nail torn partly or completely off. If the base of the nail has popped out of the skin fold, it needs to be put back or splinted to prevent the fold from scarring shut.

Chronic and repeated trauma

Picking, biting, manicure damage and repetitive sport cause nail separation, thickening and ridges. These injured nails are more prone to fungal infection.

First aid for a nail injury

1. Clean the area under running water and remove rings.
2. Press on any bleeding with a clean cloth.
3. Ice for 15 to 20 minutes, wrapped in a cloth, several times a day for the first 1 to 2 days.
4. Raise the hand or foot above heart level to reduce throbbing.
5. Take a pain reliever such as acetaminophen (paracetamol) or ibuprofen if needed, following the label dose.
6. Protect a loose nail: trim jagged edges, leave the attached part in place and tape it down with a bandage. Do not pull it off.
7. Cover an exposed nail bed with petroleum jelly and a nonstick dressing, changing it daily until the bed hardens, usually 7 to 10 days.

Treatment by a clinician

• draining a painful hematoma
• removing a loose nail to inspect and stitch the nail bed
• replacing the nail or a silicone splint under the skin fold
• treating any fracture with a splint
• antibiotics for open fractures or infected wounds
• a tetanus booster if not up to date

How long does a nail take to grow back?

A new nail may grow in with ridges, a split, or slightly thicker texture at first. Permanent deformity is more likely when the germinal matrix was damaged.

Complications

• Infection around the nail (paronychia) or of the bone
• Permanently abnormal nail: split, ridged, lifted or thickened (see irregular-appearing nails)
• Nail fold scarring, which can stop the new nail growing normally
• Ingrown nail as a damaged toenail regrows
• Fungal infection in a damaged nail

Bruise or melanoma?

A bruise from injury grows out toward the tip over months, and its leading edge moves away from the cuticle. A dark band that starts at the cuticle, widens, spreads onto the surrounding skin, or appears with no injury needs prompt review, because rarely it can be a melanoma under the nail.

Frequently asked questions

Should I drain blood under my fingernail?

If the pain is severe and the blood covers a large part of the nail, see a clinician within 48 hours. They can drain it safely with a sterile tool, which relieves pain quickly. Small, mildly painful hematomas need no treatment. Avoid DIY drainage with a heated paperclip.

My toenail fell off. What should I do?

Keep the nail bed clean, cover it with petroleum jelly and a bandage until it hardens, and wear roomy shoes. Watch for redness, pus or worsening pain. A new toenail takes 12 to 18 months to grow fully. Address the cause, such as tight or short shoes.

Should I remove a nail that is hanging off?

No. Trim sharp edges and tape the nail down. The attached part protects the nail bed and acts as a splint. If the nail base has popped out of its fold, or there is a deep cut underneath, see a clinician for repair.

How long does a black toenail take to go away?

The color does not fade; it grows out with the nail. For a toenail, that can take 6 to 12 months or longer. Often the damaged nail falls off as a new one grows beneath it. If the dark mark is not moving forward, get it checked.

Will my nail grow back normal after an injury?

Most do, especially if the nail bed and growing area were not badly damaged or were repaired. Some nails regrow with ridges, splits or lifting. Changes still present after a full regrowth cycle are usually permanent.