What Your Fingernails Reveal About Your Health You Never Knew

3.Dark Lines Beneath the Nail

Dark lines or marks under the nails can result from trauma, such as pinching your finger in a door, causing bleeding beneath the nail. However, if you notice dark streaks without any injury, it is essential to see a doctor immediately, as this can be a sign of skin cancer. Medically known as melanonychia, these dark streaks are especially concerning if they appear on a single nail. While some lines can be harmless and related to medication, pregnancy, or ethnicity, any new or changing line should be examined by a healthcare provider. Subungual melanoma, a type of skin cancer, is the most serious concern. Early detection is vital, so any unexplained dark line—especially one that gets wider or darker—should be evaluated promptly.