3.Dark Lines Beneath the Nail
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Dark lines under the nails can result from trauma, like pinching a finger and causing bleeding beneath the nail. If dark streaks appear without injury, see a doctor promptly, as this can signal skin cancer. Known as melanonychia, these streaks are more concerning if found on a single nail. Some lines are harmless and related to medication, pregnancy, or ethnicity, but any new or changing line should be checked. Subungual melanoma is the most serious concern. Early detection is critical, so any unexplained line—especially one that widens or darkens—needs prompt evaluation.
