I do not know the answer to this, but I am often a bit skeptic about this kind of stuff…. I just read about guar gum here and I guess it can have traces of soy left in it if not cleaned enough..
“Although some studies have found an allergic sensitivity to guar gum develop in a few rare individuals after working in an industrial environment involving much higher exposure than is common, almost all reported allergic reactions are due to impurities in guar gum, especially soy protein, which can make up as much as 10% of the content of commercial guar products.”
(This is from Wikipedia, which I know can’t always be trusted.)
Makes me wonder if a manufacturer can know for sure if the Xanthan Gum they buy from another company is really safe or not…. But just guessing here.