Mercury was often applied topically in the form of an ointment or rubbed onto the skin. It was also sometimes ingested in small amounts, either as a powder or in a solution. While mercury may have had some mild antiseptic properties, it was not an effective treatment for the plague. In fact, mercury is a highly toxic substance that can cause a wide range of health problems. These include kidney damage – and even death. In addition to being ineffective as a treatment for the plague, mercury was also responsible for causing numerous other health problems in patients who were treated with it. Today, mercury is not used as a treatment for any disease due to its highly toxic nature.