Food Allergies Treatment

Im not sure if that is what this is or not, just looking into what my first thoughts were…20 month old has been throwing up after drinking milk for 24 hours, however she can keep down food and other liquids, no fever. Any ideas? I am just her nanny, and her dad has a call into the doctor…just trying to get some info on milk allergy, as it was my first thought when he told me about it.