Just like in humans, allergies and sensitivities can differ widely from one cat to another so there isn't one test to guarantee that no cat will have a reaction to this product.
I would certainly discontinue immediately if your cat develops any skin symptoms and ensure to thoroughly clean the litter box and surrounding area. If symptoms persist, see your vet and investigate a different cause - a new food perhaps?
If your cat is having unusual bathroom behavior - like pooping outside of the box - without any skin or respiratory issues, it is more likely to stem from the transition process than an allergy. We recommend taking a slow approach to transitioning to a new litter; we have a great video
about this process and a blog post
for our insights on bathroom behavior.
I think we would need a bit more context to really know if it's a true allergy to the litter:
Did they just start using RGCL; if so, how many days has it been?
Has the cat's diet changed at all recently, including new treats or supplements?
Where is the reaction occurring (paws, face, ears; is it localized to one area or is it all over, etc.)?
Does the cat go outside at all?
It's entirely possible that it could be the litter, but I would say it's more likely dietary or environmental allergies first! Especially with the change of seasons right now, environmental allergies will be on the rise.
Also, if it is a localized area the cat can reach, it could even be that the cat is over-grooming due to stress? Like, if there were other changes in the home besides the new litter
Cats are easily stressed and unfortunately over grooming and eating things they shouldn’t seem to be the ways cats cope with stress! I’ve seen cats be stressed by the smallest of things, like the sound of a furnace turning on, and licking their skin/fur raw!
I’d say it’s likely the soy that would be the allergen if it’s a true allergy.