What Can Cause A Black Toenail?

Heart Disease

Heart disease is another underlying medical condition that can cause a black toenail. When there is a blockage in one or more blood vessels in the toes or foot, it can lead the toes themselves to appear purple or blue. A purple or blue netlike pattern under the skin, which may extend under the toenails, can indicate an individual has a blocked artery. If they see blue or purple lines under their nail and don't remember sustaining a nail injury, it may be a good idea to see a doctor, as lines like this can sometimes indicate heart disease. When they're related to heart disease, there tend to be other symptoms as well. Patients may experience an irregular or weak heartbeat, and they may develop a high fever.

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