Why does milk make 2yr get sick when drank, ok w/food & ok till 6mo ago w/o issue now puke *pm, diarrhea *am/pm if drank 4+oz w/any fat% lactaid is ok?

Intolerance: Some kids who tolerate milk or bovine based formula early will become intolerant later in life. Some speculate a gradual loss with age of the enzyme needed to digest the sugar in the milk (lactose). This leads to cramps & diarrhea.Those kids may tolerate small amounts without symptoms or other products like yogurt or cheese that are low in lactose.Lactaid milk is usually tolerated by this group.