Even though I am subscribed to this forum, I often miss posts, inexplicably.
I don't have all the advice for you. Yes, you are approaching it appropriately. You are observant, taking note of reactions and possible trigger sources. You are not prematurely narrowing down the possible culprits. You are contacting an allergist. You are doing everything right.
For the sake of your own sanity, I hope it is something simple, like a sesame allergy (also in Chinese food) and not a chemical allergy that you are on your own, pretty much, to discover. Your mother's hands light also have had some heavy lotion on it as well.
Please, give us an update! And good luck.
"She is a mermaid, but approach her with caution. Her mind swims at a depth most would drown in."