I've intermittantly gotten itchy hives on my arms and they seem to initially get set off after being out of doors. I recently found out I'm allergic to a lot of things. I'm moderately allergic to our beloved indoor cat and I'm allergic to some common trees that grow around here, some weeds and grasses and more. The doctor wanted to do allergy shots, but I'm afraid, because I feel I can't take antihistamines, etc. if I have a bad reaction to the allergy shots because I've noticed tachycardia (and even once a spike in blood pressure that I know of) at times taking that sort of medicine . Has anyone else with P.O.T.S. tried allergy shots? If so, how did you do?