Black spots on toenails: causes and warning signs

Blood beneath a nail may follow stubbing, running, or tight shoes and often shifts toward the tip as the nail grows. Fungal nail infection more often causes thickening, crumbling, debris, and yellow-brown discolouration, although appearance alone cannot confirm it. A pigment band may arise from the nail-producing tissue. Rarely, melanoma involving the nail presents as a dark band or patch, so the condition must be considered when pigment is unexplained or evolving.

Remove polish and photograph the whole nail in good light. Note recent trauma, footwear pressure, pain, and whether the mark moves outward with nail growth. Keep the nail trimmed straight across and wear shoes with enough toe room. Do not drill, cut, or burn through the nail, and do not try to drain blood yourself because this can cause injury or infection.

Arrange prompt assessment for a new dark mark without clear trauma, a band that widens or changes, pigment spreading onto nearby skin, nail splitting, or a spot that stays fixed while the nail grows. Sudden severe throbbing after an injury may need timely treatment by a clinician. Seek urgent help for spreading redness, pus, fever, loss of sensation, or a toe that becomes cold or unusually pale.

Tell the clinician when you first noticed the mark, whether it has moved, and whether an injury occurred. Ask if the nail needs magnified examination, testing for fungus, pressure relief after trauma, or specialist review. Mention medicines, diabetes, poor circulation, and previous pigment changes because these details can affect assessment and foot care.