Blood Under Your Nail? Subungual Hematoma in 2026 — Causes, Treatment, Healing Timeline & the Best Shoes to Protect Your Toes

Stubbing your toe against a door frame, curb, or piece of furniture is the single most common cause of subungual hematoma on the foot. The sudden deceleration forces the nail bed against the nail plate, rupturing capillaries. Tight or short shoes — especially running shoes, soccer cleats, and hiking boots — repeatedly compress the toes against the toe box, causing what runners call “black toenail.” This is actually a chronic, low-grade subungual hematoma that builds up over weeks or months.

Dropping a heavy object — like a hammer, weight plate, or can of food — onto a finger or toe generates enough force to rupture the nail bed vessels instantly. Similarly, slamming a finger in a door is a classic cause in children and adults. These injuries often produce a hematoma that covers more than 50% of the nail, and in about 15–20% of cases, there is an associated tuft fracture (a break of the distal phalanx). A crush injury warrants an X-ray if the pain is severe or if the fingertip/toe is swollen and deformed.

Long-distance runners, hikers, and soccer players frequently develop subungual hematomas on the second, third, and fourth toes. The mechanism is repetitive microtrauma: each time the foot slides forward in the shoe during downhill running or quick stops, the toes jam into the front of the shoe. Over time, this causes small bleeds that accumulate. The condition is so common among marathoners that it is colloquially called “runner’s toe” or “black toenail.” Wearing shoes half a size too large and using toe socks can dramatically reduce the incidence.

Soccer players often develop subungual hematomas from kicking the ball with the toe (a common mistake in beginners) or from being stepped on by another player’s cleats. Basketball players are vulnerable to toe jamming when landing awkwardly or when another player lands on their foot. In all cases, the risk is magnified by footwear that does not provide adequate toe protection or that fits improperly. For soccer, boots with reinforced toe caps can help; for basketball, a shoe with a wide, stable base and ample toe room is essential.

People taking anticoagulants (warfarin, apixaban, rivaroxaban) or antiplatelet drugs (aspirin, clopidogrel) are more prone to subungual hematomas after even minor trauma. The bleed is often larger and more painful because the blood does not clot as effectively. Similarly, individuals with bleeding disorders like hemophilia or von Willebrand disease may develop spontaneous subungual hematomas with no apparent injury. In these cases, even a small hematoma warrants a medical consultation, and trephination (drainage) should be performed by a healthcare professional rather than attempted at home.

Not necessarily. Most subungual hematomas can be managed at home or by a primary care provider. However, you should go to an urgent care or emergency department if: the pain is severe and relentless, the hematoma covers more than 50% of the nail, the finger/toe is deformed or swollen (possible fracture), there is a deep cut on the nail bed, or you have a bleeding disorder or take blood thinners. When in doubt, call your healthcare provider for guidance.

You can, but you need to be cautious. If the toe is painful, take a few days off to let the acute inflammation subside. When you return to activity, ensure your shoes have a wide, tall toe box and that they are laced securely to prevent foot slippage. Consider using a gel toe cap or silicone toe sleeve to cushion the injured nail. Avoid downhill running or activities that cause your toes to jam forward until the pain resolves. If the hematoma recurs, you may need to buy shoes half a size larger.

Key differences: A subungual hematoma usually has a clear history of trauma, appears as a uniform dark patch with rounded edges, and moves forward as the nail grows. Subungual melanoma often appears as a dark streak (longitudinal melanonychia) originating from the cuticle, has irregular borders, may involve the cuticle (Hutchinson sign), and does not move with nail growth. However, no home method is foolproof. Any dark nail spot without a known injury, or one that persists beyond 3 months without growing out, should be examined by a dermatologist with a dermatoscope.

No. In many cases, the nail remains attached, and the darkened area simply grows out with the nail over weeks to months. You may notice a ridge or groove in the nail as it grows. Nail loss (onychoptosis) is more likely with larger hematomas — especially those covering more than 50% of the nail — or when there is significant damage to the nail bed. If your nail does detach, keep the nail bed clean and protected; a new nail will grow in.

It is not recommended to apply nail polish to an acute subungual hematoma, especially in the first week. Nail polish traps moisture and can obscure the color and progression of the hematoma, making it harder to monitor for signs of infection or melanoma. If you want to cover the discoloration cosmetically, wait until the nail is no longer tender and the hematoma has stabilized — usually after 2–4 weeks. Use a breathable nail polish or a clear strengthener instead of opaque colors.

There is no restriction on flying with a subungual hematoma. However, changes in cabin pressure may cause a small expansion of the trapped blood, potentially increasing pain slightly during ascent or descent. If the hematoma is large and painful, having it drained before flying can provide relief. Otherwise, take acetaminophen or ibuprofen before the flight and keep the digit elevated. If you are on blood thinners, consult your doctor before traveling.