Why would a individual hold allergic criticism to drinking fresh fish but not frozen fish?

I have a friend specifically allergic to fresh fish but not frozen fish. Wondering if anyone can help how beside this. She has passed out and trouble breathing near fresh but can eat fish from grocery store contained by frozen aisle.Why would a individual hold allergic criticism to drinking fresh fish but not frozen fish?
Fresh fish has a greater karma of having curing chemicals surrounded by it.
maybe the place she's consumption at is putting a spice she's allergic to on it, but the frozen one does not have that spice. she wants to ask what they are putting on that fresh fish.
Just because you are allergic to one kind of fish does not mingy that you are allergic to all fish. Is the fresh fish like kind as the frozen fish? For example is the fresh fish salmon and the frozen fish cod? If you are comparing different fish that may be the use. If it is the same sensitive of fish, it could be the preparation of the fish - other ingredients added.
I would recommend your friend get tested to find out what she is allergic to.