Lactose is a naturally occurring simple carbohydrate, or sugar, found only in the milk of mammals.

For this reason, it is also commonly referred to as "milk sugar."

All commercial lactose is obtained from the milk of cows as a by-product of the dairy industry. 

Lactose monohydrate is added to infant formulas, packaged snacks, frozen meals, and processed COOKIEs, cakes, pastries, soups, and sauces, as well as several other foods.