17 months old sudden milk allergy?

Rosley

Can my toddler become allergic to milk suddenly? He was fine till yesterday drinking milk everyday no rash no eczema . He was seen since last 4 days and how he had hives in cheeks 1st time after drinking milk but it was not itchy went away fast. 2nd time 2 3 hrs after drinking milk those were itchy so applied Benadryl gel and it went away. Can he be allergic to milk or antibiotics reaction or viral rash?