A double coat means there is both a top (or over) coat made of tougher guard hairs and a bottom or (under) coat that is thick and soft. Breeds such as Pomeranians, Shetland Sheepdogs, Siberian Huskies, Samoyeds, Border Collies, and Retrievers are examples of double coated dogs. With a double-coated dog they need to be groomed by brushing throughout the year but most heavily done in the spring when a major shedding period occurs. As the weather warms up the thick undercoat starts to do a complete shed, it detaches from the body and is often described as molting.
The question still remains then, why not shave them and just keep them out of the sun?
Unlike people, dogs do not sweat through their skin. Dogs sweat by panting and in all but northern breeds, through the pads of the feet. Shaving them actually removes some of their natural ability to stay cool.
Once all this undercoat is removed the air can circulate between and through the hairs of the topcoat keeping the dog cool, while the topcoat keeps the skin protected from the sun. This topcoat can also protect the dog’s skin from fly and mosquito bites. Clipping short ANY double-coated breed, even once, can and often does cause serious permanent, irreversible damage to a dog’s beautiful natural coat. Their thin skin without its natural coat protection is at risk – no matter what season of the year. Shaving a double-coated dog does not stop the shedding – it only makes the hair that is shed shorter.