Where did these welts come from?

Hi everybody.  I hope everyone met up at the support group saturday and had a good time. I could not go as I have developed some type of itchy welts and rash since last week.  Went to ER, they think it may be a filler in the chewable bariatric iron vitamins I started taking recently. I think it's soy milk. Well after an injection of benadryl and something else I was sent home less itchy however, comatose.  I slept the entire day and still feel woozy today. Has anyone else had any type of rash due to vitamins or medicine after your surgery?  Hope everyone is doing well.