Q: I have just recently started running and have noticed that my toenails are getting darker. It does not hurt. What is going on?

A: “Subungual” hematomas are collections of blood that can form under the toenails due to repetitive trauma. This is a common condition in runners, due to repeated “micro-trauma” from the ends of the toes bumping against the inside of the shoes. Wearing shoes that have plenty of room in the toe box will help, as will keeping your toenails from getting too long. Chronic injury to the toenails can lead to scarring of the nail root with permanent thickening of the toenails.