its very possible that he is lactose intolerant. technically, cows milk is NOT created for humans to drink.
a lot of research is starting to show that animal proteins and fats are actually more harmful than good. i think it is the inuit tribes have the highest intake of calcium in the world, all from animal sources, and they have the highest rate of osteoperosis in the world.
nowhere in the world can you find a serious deficiency of calcium. but the milk industry doesnt want us to know that!
so even though i have no experience with lactose intolerance myself, i do want to encourage you to know that its actually more healthy to use soy or other forms of milk. and for your child, its nice cuz they dont really know anything else.
in my family we went down to skim milk, and at some point im going to start trying to mix in soy milks to get used to them slowly. the information that i have learend about animal meats and dairy is really good information, and even though it seems at face value that you need to be a vegan to be healthy, its more about just being aware that eating meat every night and drinking tons of milk just isnt that great for us. so just being aware of that and using less animal products (or just way smaller servings) and more fruits and vegetables and grains is good for our all around health! :D
another thing that is good to know for your formula fed baby is that babies usually need a bit of water to go with their formula diets. its not dangerous as some authors would have you believe (yes, any person baby or adult can overdose on water resulting in death, but thats extremely high amounts of water) its healthy and needed for formula fed babies because of the concentration of formula.
also when you start on solids, ... or anytime i guess, constipation is very common in formula fed babies. constipation is not necessarily the lack of stool, it is hard, solid, difficult to pass stool. if baby cries or has to really strain to go, its too hard. stool should always be squishy and soft even in adults.... so in order to "fix" this, a little milled flax on any type of food goes a long way to helping out! what it is is fiber, which does not get digested, but absorbs water in order to keep stool softer! :D its amazing. works like a charm! :D my son was constipated for the first time EVER, he would try to push then acted like it really hurt. i gave him some flax on his yogurt, he went within a half hour and it was nice and soft and easy to pass! :D hes 21 months old. (and was breastfed until he was 19 months.. so he has that going for him)
anyway.
this was probably OVERinformation for you, but i just wanted to let you know all this fun stuff ive been learning about food and stuff.
i hope it helps.
and again, dont feel afraid to just use soy milk, almond milk, or rice milk. however, milk is not ever needed when you have a nice healthy diet of fruits and vegetables (which are not hard to get kids to eat! :D my son loves it all, he doesnt prefer carrots, but he will eat them in subs... LOL or wraps... or macaroni and cheese... lol. its not that i HIDE them, there are chunks in the food and he asks what they are. i guess its just fun so he eats them.
anyway.
more information thats more than you asked for.
im just excited about food! :D