Chronic Hives & Angiodema

My daughter who is 12 started with spontaneous utecaria & angiodema beginning of July.
She has been admitted to hospital 2 twice because of facial swelling has no been given inhaler for cough. Has been on fentofexdine 180mg, cetirizine x40mg a day which is 3times over limit but was advised by doctor to give.
She is now on another antihistamine levocetrizine 5mg x2 & loratadine as an extra if itch is really bad.
It's affecting her daily.
We are at dermatology nxt Thursday they have said they may up dosage of current antihistamine but if does not work will consider injection(xolair)has anyone had this? If so is there big side affects does it work?
We are at allergy clinic 2 weeks today but for allergy test she would need to stop antihistamine for 5 days but letter states if she has chronic utecaria not to stop taking them. So how will we know if its an allergy that's causing it ?
Any advice would be appreciated