My Daughter Has Been Experiencing What Appears To Be An

My daughter has been experiencing what appears to be an allergic reaction, but the allergist insists she is not allergic to anything they tested her for. It starts with the end of her tongue tingling, than her tongue starts to get sore. It progresses to difficulty swallowing and the next day she has swollen lops, dry cracked skin at the corners of her mouth and a beefy red tongue with what appear to be petechiae
She does respond some what to steroids and benedryl but we want to know what is causing this