Allergic to one milk but not other?

Patient: My son is a little over a year old and has been drinking 2% milk for a couple months. We started him on Whole milk about 2 days ago and since then he has not been able to eat nor drink hardly anything. When he tries to drink I give him juice but he wants milk so i give him whole milk and he vomits but doesnt drink hardly any. He also has a fever. Can he be allergic to whole milk but not 2% milk?

Symptoms: Vomitting, fever, not eating. Only vomitting when drinking whole milk. Does fine with 2%