 [ Symptoms ] what if i get a severe reaction to milk because of my casein allergy [ Disease ] if you are diagnosed with a casein allergy your doctor may have you carry a shot of epinephrine with you in case you accidentally eat a food containing casein and suffer a reaction your doctor will show you how to give the shot you may also want to keep an over the counter antihistamine on hand to help alleviate allergy symptoms if you experience a severe allergic reaction with symptoms of anaphylaxis call 911 for emergency help and give yourself the shot to counteract the reaction until help arrives because up to one third of anaphylactic reactions can have a second wave of symptoms several hours following the initial attack you may need to be observed in a clinic or hospital for four to eight hours after the initial reaction