Health Black Lines on Nails: A Warning Sign of Aggressive Skin Cancer by Dr Natalie Singh - Health Editor May 9, 2026 by Dr Natalie Singh - Health Editor May 9, 2026 Finding a dark streak or a new spot under your fingernail or toenail is often a cause for minor concern—many people assume it’s just a bruise from a slammed door … 0 FacebookTwitterPinterestEmail