I get immunotherapy for allergies for 3 yrs now last night i broke out in hives for first time. very scary. don't know what i got into. stress?

Call your allergist : Biggest question is whether it was within minutes or a couple hours after your allergy shot (or drops); raises the possibility of anaphylaxis. Food, medication, stings also common causes. Please check with your allergist. I have had a few patients in my career on immunotherapy who have had unrelated random hives during treatment, but don't assume it.