While the prior answers are pertinent, your son's age may have some impact. Very young children (1-2 years of age) sometimes are not used to a new milk -- they've been on breast milk or infant formulas that taste different compared with cow milk. The amount of fat in the milk (whole milk versus low or non-fat) can also affect the desire of young children to drink milk. Often several attempts lead to the child eventually accepting milk.
Older children (after 3-4 years old) may avoid milk after trying it because they really do not feel well after drinking it. They may relate bloating and/or cramps that can be due to lactose intolerance. If that is the case, you can try using lactaid milk or first try cheese or yogurt to see if they are okay with these products first.
Milk allergy in infants (1-4 months old or so) is present in about 2-5% of infants and often starts with some mild blood in the stool; this typically resolves by about 1 year of age. In older kids, milk allergy developing later is relatively over diagnosed, but can occur -- usually, though, symptoms are more obvious, including skin rashes, respiratory symptoms or diarrhea.
Why do you want your son to drink milk? There are other ways to get the calcium he needs for instance brocoli has calcium in it. I always let my children choose between milk or brocoli and usually milk wins.
Hi, Have you discussed this concern with your son's pediatrician? If not, please do. Your son's doctor can test to see if your son is lactose intolerant, or if there are any other related health issues involved in your son's refusal to drink milk.
Our daughter isn't really a big fan of milk either. When she was a toddler and we were particularly concerned about her lack of milk consumption (post-nursing), we tried putting a bit of chocolate syrup in it -- which she loved and her pediatrician ok'd if in moderation (our daughter has been skinny her whole life, so it was more a dental issue that we had to be cognizant of with the addition of the chocolate). We also blended milk with frozen strawberries, another favorite of hers. She also really enjoyed macaroni and cheese, which was another way she got her daily dose of calcium. Now that she's older (in second grade), she still doesn't like drinking a glass of plain milk, but she does consume it through bowls of cereal, hot cocoa, smoothies and other food items that contain milk (such as creamy pasta sauce or Indonesian dishes her daddy makes).
The main point is that your son consumes the recommended daily dose of calcium -- whether through drinking milk or eating it.
Here's a website for those with milk allergies that lists the calcium doses for alternative sources to milk (as well as daily recommendations for calcium per age group):
Not everybody likes milk. Some people after drinking it get sick with abdominal pain, bloating, or diarrhea. If your child plainly does not milk, there are other good sources of calcium: cheese, yogurt, calcium fortified orange juice, and green leafy vegetables. If your child gets sick after drinking milk, you should have a discussion with his health care provider.