My Dad Gets Itchy Palms Than Diarrhea And Sometimes Vomiting

My dad gets itchy palms than diarrhea and sometimes vomiting and passes out. He had an allergy test done and they said they couldn't find anything but to carry an epipen or bennadrenl with him at all times. At first they thought it was food poisoning it happens almost once a month. I think it was a singles vaccine he had because this started 1 week after his vaccine but the Dr. said it would of happened instantly. What do you think?