Livedo reticularis is thought to be due to spasms of the blood vessels or a problem of the blood flow near the skin surface. It makes the skin look mottled in sort of a net pattern with clear borders. The condition most often shows up on the legs. Sometimes livedo reticularis is simply the result of being chilled. And it may occur as a side effect of certain medications. A rarer, related condition called livedo racemosa may be caused by a serious underlying condition.