Dogs hate flies for a simple reason: flies are annoying pests and dogs seem to despise them just as much as we do. We can't blame them though, deprived from having hands, dogs are pretty much at the mercy of these buzzing, pesky creatures. These leaves them with only one option: attempting to catch them with the power of their jaws.
Some dogs hate collars and this can obviously put a dent in their ability to enjoy walks and the many perks of being present in the outdoor world. Often, this peculiarity derives from underlying issues such as fear, touch sensitivity and inappropriate or insufficient handling when the dog was a puppy.