If you have a long-haired dog, the coat acts as insulation from heat as well as cold. Having your dog shaved in the summer may expose the animal to sunburn and/or heat stroke.
A dog's nails cannot always be trimmed. The 'quick', or internal blood vessel may descend almost to the point of the nail, meaning the dog would bleed if the nail was cut incorrectly.
Your long-haired dog should be combed regularly. Using a brush doesn't get down to the undercoat, which can become matted. This could cause a skin condition because the skin cannot 'breathe' properly. It would also necessitate shaving the dog. This could be unhealthy if the weather is too hot or too cold.
