Dark Nail Lines May Signal Hidden Heart Infection

Health experts are warning that unusual dark lines under fingernails—called splinter haemorrhages—may be an early sign of infective endocarditis, a rare but potentially fatal heart infection. The condition affects the inner lining of the heart and is often caused by bacteria entering the bloodstream. While the symptom may look minor or be mistaken for nail trauma, recurring lines without injury should not be ignored. Early diagnosis and treatment are crucial, as untreated endocarditis can lead to heart failure or stroke. Good hygiene, especially dental care, helps reduce the risk.