Automatic Litterbox Central

Has anybody else (non=allergic) experienced sties (Stys?) in their eyes associated with litter or scooping? I can't figure out if I'm getting them because of a specific brand of litter I'm using, or because of the dust when scooping, or what. Anybody have any points of comparison?

My info:
-- No sties, pre cats.
-- Extremely rare sties (3 per year) with Schweat Scoop.
-- None at all with crystal litter.
-- Tons and tons and tons (Argh!! 5-10 per week) when scooping store A brand unscented clumping litter
-- Many less when using store B brand clumping unscented litter in the Litter Robot (no scooping).
-- number of sties doesn't seem to correspond to handwashing or other hygiene changes.

(Yes, I know they're usually caused by Staff, which is abundant in kitty poop and am a diligent hand washer).

I'm going to try some different brands of litter, but wondered if anybody else had this problem before and was able to figure out the cause.

Thanks in advance!