Neither dog seem to notice it and I sprayed them right on their muzzles.
Animal control officers (they are now part of the police dept.) around here don't carry pepper spray anymore. They say it doesn't work on dogs. Ours carry cattle prod taser things and pistols. They use tranq darts if they have a distance and time advantage.
I heard *somewhere* and I'll be danged if I can find the reference right now, that capiscum (the hot stuff in peppers, and pepper spray) was mainly "hot" to some herbivores and omnivores. Things that tended to be closer to pure carnivore *tended* to not be sensitive or as sensitive to it, as the peppers evolved the stuff for dealing with herbivores. Might explain the lack of effectiveness on dogs, while being effective on people and grizzlies
I'm trying to find a reference to this as opposed to something I remember, and can't at the moment, so take it with a grain of salt.