I've used pepper spray on dogs a couple times, and it renders them literally senseless. They can't see or smell, and so their hearing betrays them, and they perceive any counter aggressive noise as a huge threat and will retreat away from it.

I am sure there are some animals that have such a disposition that they will try and press the attack no matter what, and will not avert after being previously exposed to such a deterrent. However they are will do so at a distinct disadvantage, and should be easy to defeat under such conditions.

The last time I sprayed a dog in the face, his eyelids clamped shut almost immediately, and he was unable to see for a solid 5 minutes because he could not open them.