When to muzzle your dog
By and large, muzzles are used to keep a dog from biting or causing injury. There are two types of muzzles: nylon (also referred to as the "groomer's muzzle") and basket.
Nylon muzzles consist of a wide strip of nylon that surrounds the dog's own muzzle, and two nylon strips that attach behind the ears to hold it in place. The nylon muzzle keeps the mouth in an almost completely closed position. Since their design restricts dogs from panting, nylon muzzles should not be used in hot weather for more than very short periods.
The basket muzzle resembles a basket that fits over the dog's own muzzle, and is normally constructed of wire or heavy plastic. Unlike nylon, the basket muzzle allows a dog to open and close his mouth. However, a dog who is wearing a basket muzzle can still cause harm by jabbing his mouth (called "muzzle punching") at a person or another dog.
So when is muzzling appropriate? Some dogs snap when having nails clipped, being brushed, or being vaccinated. A nylon muzzle is a good idea with a dog who is likely to bite when being handled by a groomer or veterinarian. Muzzles may also be used during training sessions for behavior modification. For example, if a trainer is working with a dog who has handling issues, a muzzle is used in order to ensure the trainer's safety.
Regardless of which type of muzzle is used, the dog should be acclimated to it before use. This can easily be accomplished by pairing food with the muzzle. For the nylon muzzle, stick a small treat through the bottom and let the dog place his nose into the muzzle to take the treat. For the basket muzzle, place a treat into the basket and let the dog take it.
Repeat a few times, and as the dog becomes more comfortable, gradually begin to place the muzzle on the dog, using incremental steps. For example, dog takes treat, hold for five seconds, release; as dog becomes comfortable, dog takes treat, move muzzle back over dog's muzzle, release; next step, bring straps up behind ears, release; eventually, as dog becomes comfortable, attach straps, feed through muzzle, release.
Important: Muzzling an aggressive dog can be a good management solution in a particular situation, but a muzzle should not be used as a substitute for behavior modification.