Hives and chest tightness lasting more than a day

My partner had some guacamole at a party yesterday and had what they thought was a mild sensitivity towards avocado. Previously they just got a tingling sensation in their mouth and throat. But this time they broke out in hives and have had a tight chest and heart pain for the last day and a half. The hives have gone from their face down to their chest, and have appeared on their arms now, though I think they've thinned out a little. This is all accompanied by general lethargy and muscle sorness. They also say that if they turn their ac on they get wicked cold and shivery really fast. Is this all normal of a fairly serious but not dangerous reaction? Do they just have to hunker down and wait for things to improve at all? Or should they go to an er to get checked out? They've also had some history with heart and fainting issues in the past, though it's largely under control now. They're stable right now as far as I can tell, but any advice would be greatly appreciated