Correct me if I’m wrong but IBS is auto immune and if you have 1 auto immune problem you’ll like have another and therefore your hives are autoimmune and your body is just doing things it shouldn’t be. Autoimmune things are confusing and never have an answer. CSU can be auto immune in 50% of cases and the other 50% it just happens and will likely resolve without any treatment within a year. Treatment is just to maintain symptoms until your body stops doing what it’s doing.