I don't block squares. Putting them together seems to take care of any unevenness.
I live with a cat, but he doesn't come into my room, where I do most of my crocheting, and rarely goes into the room where I do a bit. My room and clothes sometimes have some kind of chicken detritus, usually bits of straw.
I'd not met anyone before with a guinea pig allergy. I have a life-threatening allergy to rabbits. I think they're related.
I don't have any rabbits either and if the cat is rarely around there's not much chance of dander coating the squares terribly if at all.

And, no rabbits are not related to guinea pigs. I used to bring in rabbits to my science classes and I taught about them in detail. Until 1912 it was thought that rabbits were also a rodent (like guinea pigs). They are now known as lagomorphs and are related to Pikas which kind of look a little like guinea pigs. Hares are also part of the lagomorph order.