What causes bruising under a toenail?

A tight shoe, running, a dropped object, or a stubbing injury can damage tiny blood vessels beneath the nail. Blood then appears red, purple, brown, or black and may cause throbbing pressure. The colour often moves toward the tip as the nail grows. A dark streak that does not move with nail growth, begins without injury, or extends onto nearby skin needs assessment because pigment disorders can mimic bruising.

A yellow, crumbly, thickened, or lifting nail points more toward infection or ongoing nail damage than fresh blood. Pain level and the timing of the mark help a clinician interpret it.

Wear roomy footwear, protect the toe, and keep the nail clean and dry. Do not pierce or drain the nail yourself. For a recent minor injury, a wrapped cold pack and elevation may reduce discomfort. A clinician can decide whether pressure relief or Nail Surgery is appropriate, particularly when pain is intense or the blood covers much of the nail.

Seek prompt care after a crush injury, severe throbbing pain, a deep cut, deformity, numbness, or inability to bear weight. Arrange review if redness, warmth, swelling, pus, or fever develops, or if the dark area does not grow out. A new unexplained streak, pigment reaching the surrounding skin, or a mark unlike your other nails warrants dermatology assessment.

Ask whether the mark is a subungual haematoma, infection, or pigment; whether an X-ray or nail examination is needed; and how to protect the toe while the nail grows.