Mrs Brown, I have total empathy with your daughter. Mine started with a household flea spray and progressed from there.
You need to ask your GP for allergy testing at the hospital. It can take sometime to get an appointment though. When it does, shower with ONLY water, no soaps, creams, anything else you can think of. The process is having allergy causing substances put, normally on your back, to have small amounts of any suspicious substance put onto your body and marked with what the substance is. You cannot take a shower or bath for the time being. Mine was started on a Monday, fairly normal day since the tests are done over 5 consecutive days. On the Wednesday you go to see an allergy nurse who looks at any reactions and remarks the tests. Body sweat and clothing can and probably will help to erase the markings. On the Friday the Consultant takes a good look. Then you get your diagnosis. Don't be surprised if you get multiple reactions. I had 42 done, did wonder if it was going over board a bit, but I badly reacted to 17.
Re your daughter and anaphalxsis. Does she now carry an epipen/ If not, demand that she has one via your GP. My experience was thankfully when I was already in hospital. Latex and I really loath each other!
Good luck