How to know if my son is allergic to dairy?

Lactose Intolerance: Lactose intolerance occurs in people who can't digest lactose, the sugar found in milk & other dairy products, such as ice cream and soft cheeses. People who are lactose intolerant don't make enough lactase, a natural enzyme made by your intestinal tract that digests lactose. Symptoms include gas, bloating, stomach cramps, and diarrhea.

Symptoms: Dairy allergy can have subtle symptoms such as an aggravating rash or more profound symptoms like vomiting, diarrhea, eczema, nausea, gas, abdominal pain and or blood in the stools. There are allergy test that a primary care physician can do or an allergist can do a skin or blood tests. Usually it is the protein in milk that people are allergy to. Others are simply intolerant, lacking lactase.