The science of dog fur and why cutting is not cool

When the stifling heat and sweaty humidity of summer comes crushing down on you, imagine putting on a fur coat.

It’s hard to be a dog during the dog days of summer. The heat of July and August can be uncomfortable for Fido, at best – at worst, tragic. For some dog owners, it may seem intuitive to take off that fur.

Dog fur is complicated. Many dogs – even some short-haired breeds – have two layers of hair, an undercoat and an overcoat. In winter, two fur coats is a great idea. In summer it may seem unbearable, but dogs do not experience heat the same way people do.

“Dogs do not sweat through their skin,” said Dr. Deborah Mandell of the University of Pennsylvania veterinary hospital. “They get rid of heat by panting, or through the pads of their paws. Clipping is not going to give them extra release.”

Just the opposite: shaving a dog can make him hotter. Those layers of dog fur work together as an insulation system, like a Thermos.

“It can trap hot or cold. If they are in an air-conditioned house, it keeps a layer of cold air next to their skin when they go outside. So it still protects in the summer,” said Mandell, who says dog fur should never be cut because a haircut can do more harm than good.

Owners, sometimes, do not like that advice.

“The same is true of veterinarians,” said Dr. Michael Cohen, of Center City Veterinary Hospital. “Veterinarians have vastly different opinions on this.”

Cohen has clients who swear up and down that their dog is happier and cooler after having been shaved down. Anecdotal evidence, based on experience, suggests haircuts could make a difference.

“On the other hand, I see dogs – Pomeranians and arctic breeds, like Huskies – whose hair will not grow back correctly,” said Cohen.

As it happens, I own a dog with a double coat, a Great Pyrenees mix named Watson. Pyrs are a kind of mountain dog originally bred to guard sheep on a French mountainside, not walk the mean streets of Philadelphia in summer. In an attempt to make him more comfortable in the city, I brought him to a dog groomer.

“When we go downstairs, he’s going to get a good blowout first, to blow out all the loose hairs. That will loosen the mattes in the back,” said Courtney Golden, at Doggie Style in South Philadelphia, while running her fingers through Watson’s fur. As much as I try to stay on top of his grooming, Watson still gets mattes in his fur, and his hair is all over my house.

“It’s up to you,” said Golden. “People come in all the time and know they don’t want to deal with the hair. I would recommend a light trim on him.”

As with most aspects of the domestic dog, its health is directly tied to the behavior of its owner. Regardless of a shave, a light trim, or a blowout, it’s more important for the owner to manage the dog’s activity. Whether on a French mountainside or South Philly pavement: it’s normal to be lazy in August.

“These dogs are not going to be running around on trails in daylight with no shade. They are going to go under a tree, maybe near a nice cool stream, and chill out,” said Dr. Cohen. “They can be here with no problems long as we don’t force them on a run with no shade.”

Most cases of heat stroke in dogs do not happen in late summer, but in the cooler temperatures of spring. Cohen says as soon as the days warm up, owners itching to get outside take their dogs running before they have adapted to the season. It’s the dogs that suffer from the owner’s enthusiasm.