Pepper spray will not hurt a dog as long as the pepper spray is washed off the dogs face and eyes in time.
Pepper spray is a good way to stop a dock attack if the dog is being aggressive towards you.
I have used pepper spray on dogs before when I have been walking around and had dogs chase after me for no reason.
I sprayed the dog with pepper spray and it immediately stopped the dog attack.
I always keep pepper spray on me and have it handy on my waistband of my belt so that I can get to the pepper spray for either dog attacks, human attacks or if somebody else is being attacked.
I also carry a taser and had to use it once to stop an older lady getting attacked by a guy wearing a mask trying to steal her purse.
I used the taser which immediately stopped him and he took off after he was able to get back up.