Milk is made lactose free by adding the lactase enzyme to regular milk. Lactase breaks down lactose into the two simple sugars--galactose and glucose--which combine to form it. The resulting milk is usually sweeter than regular milk due to the fact that these two sugars are sweeter separately than they are when combined into lactose.
Many other food products such as cottage cheese, ice cream and eggnog are also made lactose free using the same method. Lactose-free products are used primarily by people suffering from lactose intolerance.
In people suffering from lactose intolerance, the body fails to produce enough of the lactase enzyme needed to break down lactose, resulting in gastrointestinal difficulties such as gas, bloating, cramping and diarrhea. Lactose can be found in many dairy products as well as in many other foods that use dairy ingredients.