"My dog has never bit anyone, why should I have a muzzle?"
There are many reasons why every pet parent should invest in a muzzle.
Pet professionals will agree, when in pain even the most docile, gentlest of pooches or kitties can bite (even their owners). It's just their way of saying, "I am in pain, I don't want you to touch me!"
So let's say your dog has an unfortunate run-in with a pricker bush and you need to pull out the stuck barb. Every time you attempt to get close to that area, it growls or shows you teeth, a muzzle would ensure that you stay safe while administering first aid.
Our Sally really hates to getting her nails trimmed. I am almost certain she would never bite us, but just don't want to take any chances. Slipping on a muzzle with a slather some peanut butter inside for a strong distraction helps tremendously.
Your pet is clearly in distress, using a muzzle before conducting a full assessment will help prevent injuries to you. This first step in first aid is to ensure YOUR safety!
When Greyhounds run in groups, you will always see them wearing muzzles. It doesn't mean they're vicious. (They're generally the total opposite!) During the heat of the run, they become playful and excited, therefore Greys are known to 'nip' each other. Because of their thin, delicate skin a small nick can easily become a long gash that may need stitches. You will see them with a style of muzzle called "basket muzzle". This would be ideal for when your dog needs to eat and drink or when it's warm and they need to cool themselves.
If you were to ask any cat owner what their cute little fur balls hate the most, baths and nail clipping would be at the top of the list. You can prevent the cat from escaping by using the burrito blanket method but it does nothing to prevent bites. Why chance getting hurt when you can use a soft, mesh muzzle designed for feline faces? Contrary to your first instinctual response, "oh no, my cat would absolutely freak out even more with a muzzle!" But by covering the entire face, you may find it actually has the total opposite reaction. Think of how people use blinders for horses, cutting the visual stimulation can have a calming effect.
There are many muzzle designs, and other than pet preference, the features of the face will determine which one works best for your pet. As mentioned before, dog basket muzzles are best for longer faces. This will allow them to breathe normally, drink water, even eat. There are muzzles especially designed for brachycephalic dog breeds (Pugs, Boston Terriers, etc)
Some things to remember about muzzles:
Never use them if the pet is choking, experiencing trouble breathing, or having seizures.
Always approach using a soothing, calm voice. Practice using the muzzle as much as possible to desensitize them to a foreign object on their face.
"Does anyone have a map?"
"Life without traffic lights"