Mercury (Hg) is a silvery-white liquid metal, commonly known as quicksilver. It is fluid and easily evaporates at room temperature. Mercury and its compounds are toxic. Excessive use or prolonged use can cause mercury poisoning. Metallic mercury is generally not used as a medicine. It is only used as a raw material for fillings in dentistry, and is used in a state of combination of mercury and other metal materials, which is not absorbed by the body. Common mercury compounds include mercuric sulfide, mercuric chloride, mercurous chloride, mercuric oxide, and organic mercury pesticides. There are many mercury-containing drugs, such as mercuric chloride, cinnabar, Dashengdan, Xiaoshengdan, mercury powder, red mercury, etc. Some traditional Chinese medicines also contain mercury compounds, mostly mercuric oxide. Mercury poisoning in children is mainly caused by accidental ingestion or overdose of mercury-containing drugs.