Nitrite is a general term for a class of inorganic compounds, mainly referring to sodium nitrite, which is easily soluble in water. Nitrate and nitrite, which are closely related in human life, produce nitrite when food is left for a long time, and nitrite can cause symptoms of poisoning. Infants and children are particularly sensitive to nitrites and can develop methemoglobinemia. When infants consume foods with high nitrite or nitrate concentrations, they can suffer from hypoxia, cyanosis and even death. Positive nitrite in urine is often closely related to urinary tract infections, and a positive nitrite often indicates the occurrence of a urinary tract infection. Nitrite intake needs to be controlled and the amount of nitrite ingested into the body should be controlled under normal circumstances.