When a Big Toenail Looks Bruised

Trauma can cause blood to collect beneath the nail, producing red, purple, brown or black discolouration. The nail may feel tender and can loosen as a replacement grows, but not every dark mark is a bruise.

A recent dropped object, stubbed toe, long walk or tight shoe supports a traumatic cause. With nail growth, a bruise should gradually move towards the free edge. Pigment that begins without injury, forms a lengthwise band, widens near the cuticle, extends onto nearby skin or stays fixed deserves dermatology assessment.

Other causes of dark colour include fungal change, external staining and inflammatory nail disease. Visual inspection may narrow the possibilities, while dermoscopy or a nail sample may be considered according to the pattern.

Rest the toe, use a wrapped cool pack for short intervals and wear roomy footwear that does not press on the nail. Keep the area clean and dry. Trim only detached nail at the free edge; do not pull at a nail that remains attached.

Do not pierce or burn a hole through the nail at home. If trapped blood is causing strong pressure pain after a recent injury, a clinician can decide whether sterile drainage is appropriate and check for a deeper wound or fracture.

Seek urgent assessment after a crushing injury, for severe or increasing pain, a deep cut, uncontrolled bleeding, a visibly misshapen toe or inability to bear weight. Spreading redness, warmth, swelling, pus or fever can signal infection.

Arrange a dermatology review for unexplained pigment, colour that does not travel outward with nail growth, a changing dark band or pigment reaching the skin beside the nail. People with diabetes, poor circulation or reduced sensation should seek early advice after any nail injury.

Describe the injury and timing, then ask whether the colour behaves like trapped blood, whether the bone or nail bed needs checking, and how to protect a loose nail. For pigment without trauma, ask whether dermoscopic examination or follow-up photographs would help monitor its movement and shape.