Hi M.-
Ditto what the other posters said. I would stop giving milk until you get to an allergist. Your pediatrician would be able to give you a referral. My son has a milk protein allergy, and since I'm allergic to soy, we started him at 3 months on a "hypoallergenic, amino acid-based formula". There are two on the market called Neocate and Elecare. They are elemental formulas for children with "gastrointestinal tract impairment" but also for kids with a milk protein allergy. These formulas have made all the difference for my son.
Until you figure things out, you are risking having problems EVERY time you give your son dairy, particularly if he has a consitent reaction.
It's absolutely not the end of the world for a child not to have dairy. Your pediatrician would advise you on things to do to ensure a balanced diet for your son.
My son wouldn't take milk from a sippy cup for a long time, so I started adding like 1/8 teaspoon of grape kool-aid to his cup of formula. I know, I know, but I knew it wasa only temporary and once he started taking milk consitently, I just weaned it. He liked the taste of grape Motrin, so I just stuck with that flavor. Start to finish, it only took about a week, week and a half tops.
Good luck!!
J.
Good luck!