Dog owners are divided in their thoughts of using dog muzzles. But, experts say that muzzles are beneficial for the dog in means of safety and that every dog owner will find himself in a situation to use a dog barking mask. I must point out that a dog should not wear muzzle for very short or very long time since it affects eating, drinking and panting. There are few situations where you should put a dog muzzle, for example when your dog is injured, is in pain or fear; when the dog is aggressive and has bitten other dog or person before; when grooming and when you are walking somewhere where there might be dog poison left.
Source: https://www.thevetshed.com.au/dogs/training-equipment/muzzles/
