R.G.
L.,
Milk issues can present themselves in the following ways:
Loose stools (possibly containing blood), vomiting, gagging, refusing food, irritability or colic, and skin rashes. Most children will outgrow this form of allergy by 2 years of age.
Also, irritability, vomiting, wheezing, swelling, hives, other itchy bumps on the skin, and bloody diarrhea can occur within a short period of time after consuming milk.
Remember, animal milk is not a necessary part of the human diet. Try using other foods for their calcium needs if that's your reason for wanting to include milk into their diet.
Here is an AWESOME list of non dairy sources of calcium:
http://www.healthatoz.com/healthatoz/Atoz/common/standard...
While I realize your original question was not one about dairy alternatives, I wanted to show you that you do not need to include dairy in your child's diet just because.
Best of luck.