I've had a lot of experience with this over the past year, building up from a reaction to a lotion in january to this summer when i would have massive hives all over my body for no reason even while on 3 different medications treating for allergies, with angiodema (swelling) on face and hands
if you have similar issues, talk to an allergist/immunologist about Chronic Urticaria. there are a lot of different causes, Ideopathic means they can't find the reason but I have the Autoimmune kind, meaning it's my immune system attacking itself. Talk to your doctor and maybe get some bloodwork done, cause it's a bitch to try to deal with on your own.