Symptoms of milk allergies may manifest immediately following ingestion or a while thereafter. Mild reactions may only include a handful of symptoms, but there's no guarantee that the next episode won't be more severe.;Some common immediate symptoms include the following. Vomiting Diarrhea Puffy, itchy eyes Hives Rash Coughing Wheezing Impaired breathing Loss of consciousness Milk allergy symptoms that may occur hours or even days later include the following. Rejecting food Irritability Bloody or non-bloody diarrhea Vomiting/gagging Rash, including eczema If you suspect that your baby has a milk allergy, it's essential that you discuss formula options and preventative measures with his doctor.