As humans, we have a very obvious reaction to a hot day or an intense gym session: we sweat. It covers our skin, evaporates, and cools us down. But have you ever noticed that your canine companion doesn't get damp with perspiration after a game of fetch? That is because a dog's ability to manage heat is entirely different from our own.

While humans rely heavily on sweating, dogs utilize a complex biological system to maintain a safe internal temperature. Understanding this system is vital for any owner, especially when the seasons change. Whether facing extreme heat or freezing cold temperatures, your dog’s body is constantly working to keep them comfortable and safe.

Keeping warm in winter

Before discussing how a dog cools down, it is helpful to understand how they generate and retain warmth. When the ambient temperature drops, a dog’s body has several defence mechanisms to prevent hypothermia.

The insulation of the coat

The first line of defence against the cold is, naturally, the dog's coat. Fur works somewhat like a thermos flask; it traps air close to the dog's skin. This layer of trapped air is warmed by the dog’s body heat and acts as an insulating barrier against the cold outside air.

This is particularly effective in double coated dogs such as Huskies, Golden Retrievers, and German Shepherds. These breeds have a soft, dense undercoat for insulation and a coarser outer coat for weather protection. Single coated dogs (like Greyhounds or Whippets) or mixed breed dogs with thin hair lack this dense underlayer, making them much more susceptible to the cold.

Piloerection

You might have noticed your dog's hackles rising when they are alert, but this also happens when they are cold. This process, known as piloerection, causes the hair follicles to stand upright. By fluffing up the fur, the coat increases its thickness, allowing it to trap more warm air against the skin.

Shivering and circulation

If the coat isn't enough, the body takes more active measures. Shivering is an involuntary muscle response. Rapid muscle contractions generate metabolic heat, which helps raise the body temperature.

Simultaneously, the blood vessels in the extremities (like the paws, ears, and tail) constrict. This reduces blood flow to these outer areas, keeping the warm blood concentrated around the vital organs in the body's core.

Do dogs sweat?

A common misconception is that dogs do not sweat at all. In reality, dogs sweat, but not in the way we do. They have sweat glands, known as merocrine glands, located specifically in their paw pads.

If you have ever seen damp footprints on the floor on a hot day or during a stressful visit to the vet, that is the dog sweating. However, because the surface area of the paws is so small compared to the rest of the dog's body, this serves very little purpose for cooling. It is believed that this sweating function is actually designed to provide traction on surfaces rather than for temperature regulation.

Panting: The primary method

Since sweating through the paws is insufficient, the primary method dogs use to lose heat is panting.

Panting allows for rapid evaporation of moisture from the lining of the mouth, the tongue, and the upper respiratory tract. As the dog inhales and exhales quickly, the moist air inside the body evaporates, which cools the blood circulating through the capillaries in the nose and mouth. This cooler blood then circulates back through the body, lowering the overall temperature.

It is a highly efficient system, but it has limitations. Excessive panting that is heavy, loud, or accompanied by a dark red tongue can be a sign that the dog is struggling to cope with the heat and may be approaching dangerous levels of heat stress.

Breed variations

Not all dogs can pant efficiently. Brachycephalic breeds—those with flat faces like Pugs, French Bulldogs, and Boxers—have shortened airways. This anatomical structure makes it much harder for them to move air back and forth over their respiratory tissues. Consequently, these breeds are at a much higher risk of heatstroke because they cannot regulate their body temperature as effectively as long-nosed breeds.

Vasodilation: Using the blood vessels

Alongside panting, dogs rely on a process called vasodilation. When a dog is hot, the blood vessels in their face and ears expand (dilate). This brings hot blood closer to the surface of the skin, allowing the heat to radiate away into the environment.

This is why a dog's ears often feel hot to the touch after exercise or on a warm weather day. The body is actively trying to push heat out through these thin-skinned areas.

Managing hot weather and heat risks

Because dogs regulate their temperature differently than us, they are more prone to overheating. Heat stroke is a life-threatening condition that can occur in just minutes. As a responsible owner, there are several ways you can help your dog stay cool.

Avoid hot cars

The most critical rule of dog ownership is never to leave a dog in a parked car. Even with windows cracked, a car acts like a greenhouse. On a mild 22°C day, the temperature inside a car can soar to 47°C within an hour. In hotter parts of the year, this happens even faster. Since dogs rely on panting, and panting relies on cool air circulation, a hot, stagnant car renders their cooling mechanism useless.

Limit exercise in extreme heat

During the summer, try to walk your dog in the early morning or late evening when the air is cooler. Hot pavement can burn sensitive paw pads, and vigorous exercise in a hot environment can cause their temperature to spike rapidly.

Create cool spaces

Ensure your dog always has access to shade and fresh water. If your home gets warm, consider using cooling mats or keeping the dog in a room with a tiled floor. Cooling products like vests that you soak in water can also help by mimicking the effect of sweating on the dog's coat.

Water play

Most dogs love cool water. A paddling pool in the garden or a swim in a safe lake helps conduct heat away from the body much faster than air. You can also use damp towels on their stomach or inner thighs to help them cool down, but ensure the water is cool, not freezing, to avoid shocking the system.

When to seek help

It is vital to monitor your dog's overall health and behaviour year round. If you suspect your dog has overheated—indicated by heavy panting, drooling, lethargy, or collapse—you must move them to a cool area and contact a vet immediately.

By understanding how do dogs regulate their body temperature, you can better prepare for the changing seasons. From the insulating power of their fur in winter to the evaporative cooling of panting in summer, your dog's body is a marvel of nature. However, unlike humans, they cannot change their clothing or grab a cold drink from the fridge themselves. They rely on you to keep their environment safe.