Dogs overheat much easier than people

Aside from having a fur coat that insulates dog’s to core temperatures higher than humans, they also lack an integral self-cooling component that humans have – the ability to sweat.  As a human’s core temperature begins to rise to levels above ideal homeostasis, apocrine glands deep in the skin excrete sweat.  Sweat cools the body as it evaporates from the skin in a process that is similar to pouring water on a hot surface.

Apart from a small, limited number of apocrine glands in the paw pads, dogs generally lack apocrine glands and therefore have a very limited ability to sweat.  Thus, the dog’s only modality to vent off excessive core body heat is to pant.

While panting is works reduce body heat, it is not nearly as efficient as sweating as a means to get rid of excess core body heat, putting dogs at a much higher risk of heat stress than humans.  If not recognized quickly enough and the dog is not removed from the activity and/or ambient temperature that is causing him to overheat, heat stroke can then set in, which is a life-threatening emergency.

Certain breeds are especially prone to heat stroke, beginning with the Spitz breed classification. There are about 50-70 types of Spitz breed dogs, all originating from the Arctic.  Some well-known Spitz breeds include Akita, Siberian Husky, Pomeranian, Alaskan Malamute, and Shiba Inu dogs.

What Spitz breed dogs all have in common is an adaptation to harsh northern climates.  This includes thick hair coats with a water-resistant outer layer, and a deep under coat that keeps them dry and insulated.  Popular all over the world including in temperate, subtropical, and even tropical climates, being poorly adapted to warm temperatures, they are very prone to heat stroke in comparison to other breeds. Always remember that a comfortable temperature for a Spitz breed dog is 17 degrees in the snow.

The other class of dogs that are especially prone to heat stroke is brachycephalic dogs.  “Brachycephalic” dogs refers to dog breeds that have a pushed in face.  This would include French Bulldog, English Bulldog, Boston Terrier, Boxer, Pug, and Shih Tzu.

The pushed in face conformation has a number of consequences that make breathing more difficult for the dog.  They commonly have narrow slits for nostrils, a condition we term “stenotic nares.”  The nasal sinus has more acute turns and narrower diameter creating more turbulent airflow.  Brachycephalic breeds commonly have elongated soft palates that can occlude the main airway, and commonly have narrow tracheas.

The net result of all of this is a reduced ability to breathe efficiently and consequently, a reduced ability to pant.  Not being able to pant efficiently translates to a lessened ability to cool effectively, leading to a higher predisposition to heat stroke.

Signs that a dog is experiencing heat stress include:

• Severely extended and dropped tongue, what I term the “power pant” (see the image at the beginning of this chapter
• Distressed, noisy breathing
• Excessive salivation
• Severely red gums and tongue
• Agitation

Signs of heat stroke include weakness/incoordination, fainting, seizure, and sudden acute death.

At the early stage of heat stress, a dogs should be removed from the activity/high temperature immediately, and brought into shade at the very least, ideally brought inside to an air-conditioned space, offered water, and be encouraged to settle down.  Once a dog is showing signs of heat stroke, it is often too late, and you should seek veterinary care as soon as possible.

Dr. Roger Welton is a practicing veterinarian and highly regarded media personality through a number of topics and platforms. He is the author of his top selling memoir The Man In The White Coat: A Veterinarian’s Tail Of Love. In addition to this writing this blog, Dr. Welton also hosts the popular Space Coast Pet Podcast.  He is the CEO and chief attending veterinarian of Premier Veterinary Care in Viera, FL.