Dear Dr. John,

Our dog is a long-haired mutt. To look at him, one would think he was a mix of a spaniel, retriever, and a shepherd. During the recent heat waves, he seemed to be uncomfortable so we took him to a groomer and had him shaved down. Now we hear that we might have made a mistake. Is that true? The groomer didn’t say anything to caution us against having him shaved. Why is it harmful to shave down a thick-coated dog in the summer months when the temperatures get so hot? He does seem somewhat more comfortable on some of these hotter days. If he does overheat, what should we look for?

— S.H.

Dear S.H.,

What you heard is correct in that long-haired breeds of dogs should not be shaved down when the outside temperatures get too hot. Their long hair and often thick double coats serve as insulation and actually protects them from the heat in the summer as well as the cold in the winter. Shaving them can make them more at risk for heat stroke and even sunburn by removing the insulating layers of their coat.

Some breeds can do well with being shaved or getting haircuts and these are the breeds that do have hair that grows and needs to be cut or else it gets too long.

The signs of a dog that is overheating include unusually excess panting and rapid breathing, drooling, lethargy or disorientation, and if their gums are bright red. If things get worse, this can lead to vomiting, diarrhea, and seizures before collapse. Death can occur.

Any signs like this must be addressed immediately. Cool wet towels, placing the dog in cool water, and providing water to drink are helpful but if there is any doubt, the dog should be taken to and seen by a veterinarian.

The best thing any dog owner can do to prevent heat stroke is ensure that dogs have plenty of cool shade, access to water, limit their exercise, and aren’t exposed to excessive heat for too long. Most importantly, do not leave a dog in a parked car in the sun. Your dog’s coat should grow back uneventfully. Just don’t do the same next year.

Dr. John de Jong is President of the World Veterinary Association. He owns and operates the Boston Mobile Veterinary Clinic and can be reached at 781-899-9994.