What Your Nails Reveal About Your Health: Surprising Signs You Shouldn’t Ignore

3.Dark Lines Beneath the Nail

Dark lines under nails can result from trauma, like catching your finger in a door, causing bleeding. If you see dark streaks with no injury, see a doctor right away, as they can be a sign of skin cancer. Called melanonychia, these streaks are especially concerning if they appear on just one nail. Some lines are harmless and linked to medication, pregnancy, or skin tone, but any new or changing streak should be checked. Subungual melanoma, a form of skin cancer, is the most serious risk. Early detection is vital, so any unexplained dark line—especially one that widens or darkens—needs prompt attention.