Oh your poor child…
No kid should have to go thru this.
Reactions to different brands depends on lots of things, how it’s prepared and if it’s mixed properly, the temperature its kept at, and well ever so many things.
I was on Gammagard which has a saline mixer, and am now on Gammunex which has a sucrose mixer. So far, knock wood I’ve had far less side effect issues to the latter one. But that is me, not your Kevin. Do make a point of talking to your doc[s] about this issue and your concerns. It may mean even more tests to get the brand/type of IVIG that works best, but, I should think it’s worth it.
I wish I could hug your Kevin’s pains away, but let him know that there are probably lots of good people here wanting to do it!