Suggest Treatment For Allergic Reaction To Fentanyl Drug

Question: My daughter had a scope of her stomach and was given fentanyl as anesthetic, she had a reaction which took almost 2 hours to rectify: extreme itching of face, nose, lips with no apparent rash at first, would not wake, hyperventilation. She is 16 and was there for stomach issues, vomiting, not keeping water/food down, discovered H-pylori. Have not started prev pac due to trying to get stomach healed and ready for prev-pak and this issue... Now a week later she is having recurring itching of face with rash. She is on valium 2mg and citrizine, somewhat relaxes her but itching continues. Allergist who was consulted don't think it is a true allergy…can you help? Nobody is entertaining the idea that this could be a lingering result of the anesthesia fentanyl, why?

But it is possible to linger perhaps in lipids for several weeks although rare? They gave her antidote to reverse fentanyl and benedryl in IV at time of reaction. I read anout nalexone in my own research but her docs are not going down this path insisting it cannot be the fentanyl. They are now ordering EEG, will this tell us if it is mu receptor?

Thank you. Since this conversation, they have put her on Zantac, Valium, and Citrizil. She is getting some relief but it is not abating entirely. Still no results back from the Triptase test…not sure why it is taking so long (5 days now). We are being referred to U of M Mott Children's Hosp for further testing and evaluation. They never did do the EEJ. It is just so odd that this is the identical reaction to what happened under anesthesia, with itch occurring in the same location each time localized to face but intensely under nose and at lips. We are now three 17 days out from the anesthesia. Frustrating. Could the H-pylori be causing it?
Not sure if I mentioned that when she was returned to her room to recover from anesthesia/scope, they said she would awake in 5 or 10 minutes, she did not awake for the full 2 hours afterwards, thrashing and crying out about the itch but eyes closed the entire time, hyperventilating etc. After several hours, with no medications helping, the anesthesiologist opened her eyes with his hand (I saw her eyes rolled back in her head as I was trying to comfort her), when he did this with one eye they both popped open immediately and she was wide eyed and went from hyperventilation to a sudden stop…then normal breathing, wondering why there were so many doctors and nurses at her bedside. She does not recall the incident at all.
Also, she is adopted, we don't know much about her family history except that there was drug addiction from before she was born. Could this somehow be a factor with the opiate?