Membrane fractionation is the process by which lactose is removed from milk; the lactose is isolated within the milk and is then mechanically separated from the other properties of the milk. This process allows people who are not able to tolerate lactose to enjoy milk and the benefits that it provides.
People who are lactose intolerant have a different issue than people who have a milk allergy. People who cannot tolerate lactose are simply not able to properly digest the lactose sugars that are present in milk. Lactose intolerant people do not produce enough lactase, the enzyme required to break down lactose. Lactose is not completely necessary for the nutrition that milk provides, so they can be safely removed from milk without the sacrificing nutrition. People who are allergic to milk have a true allergy to all of the properties that are present in milk.
Lactose intolerance does not always mean that a person should stay completely away from dairy products. Some dairy products such as butter and cheese are strained enough that the lactose will not affect the people who eat them. Many people who are lactose intolerant can also drink skim milk. There are many milk and dairy products that are available with the lactose taken out of them.