the major concern comes down to the dog’s collar fitting properly.
If the collar is too loose, the dog may be able to slip one of its limbs under the collar, or even get its mouth trapped on the collar.
The dog’s subsequent reaction to being stuck can cause him to injure himself.
Likewise, if the collar is too tight, there is a higher risk for the dog to have hair loss in the affected areas and this increases the risk for infection.
In extreme situations, the collar can even cut into the dog’s neck if it’s too tight. This is unfortunately common in neglect cases.
Many vets recommend rotating through different collars and checking your pet regularly to make sure that their collar is fitting appropriately and not adding risk for injury.
They also say that choosing to remove the collar when it is safe is a good way to allow the skin in the area to breathe.
An article on PetMD, called Ways Collars Can Harm your Dog, goes into great detail on potential collar-related injuries.