There is SOME reaction to everything. Yes, someone in the world will have a "reaction" to vinegar and alum. If anyone is ever that worried about it then they wouldn't even breath, cause everyone who has ever breathed has died.
My point is that ya gotta live, and any company putting out a product is gonna make sure your alright. If alum and vinegar was a problem, we'd see it on the news, papers and warning labels all over!
Don't sweat the small stuff. There are thousands of other things to worry about.