Lactase is a protease that can hydrolyze lactose into glucose and galactose, which can turn lactose with low sweetness into monosaccharides with higher sweetness, and it is an enzyme secreted by the small intestine that can help digestion. In food, it is often used in the production of ice cream and light condensed milk. In medicine, it is often used in patients who are lactose intolerant. The disease is often associated with genetic or congenital factors; lack of lactase in this patient tends to cause intestinal flora imbalance and can affect the intelligence of children. Consumption of low-lactose dairy products or taking lactase tablets can be used to treat lactose intolerance.