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What the dog nose.

Aug 24, 2023
Dog nose, training and behaviour


What the dog nose


Have you ever just looked at your dog’s nose and thought, how’s that work? I’m fascinated by how intricate and amazing their sense of smell is and thought I’d bore you with some ‘light’ info about the bits of their nose you can see, the external gubbins.

Grab a coffee, get your dog close and let’s see what the dog nose.



The Rhinarium


Let’s start with the Rhinarium, the bit you’ve most likely kissed, the bit on the end.

It's that leathery, often moist surface surrounding the nostrils, (the fingerprint of the dog), and it plays an essential role in scent detection, environmental interpretation, and even social communication.




The rhinarium is the hairless skin area around the nostrils that is often cooler than the rest of the body and has a moist, smooshy texture. This unique surface contains special glands that secrete mucus, making it the perfect environment for trapping scent particles.


Cellular Construction


This is a bit sciency but in for a penny, in for a pound.  The Rhinarium is made up of layers of layers of epithelial cells and a vast network of capillaries and nerve endings allowing it to be extremely sensitive to changes in temperature, humidity, and of course, scent.

These cells enable your dog to be experts at identifying and interpreting various chemical compounds found in the air.

Think of sniffer dogs and how they detect the slightest compound they’re trained to search for.


Olfactory Superiority


The moist environment of the rhinarium enhances a dog's sense of smell by trapping odour molecules. When a dog sniffs, air (and smell particles) is drawn through the nostrils, passing over the moist surface of the rhinarium. This allows the olfactory receptors located further back inside the nasal cavity to have a stronger set of information to interpret.


Thermal Sensing


Now this blew my mind! The rhinarium is cooler than other parts of the body, just touch it and you’ll see, this helps in evaporative cooling, an essential part of the body for animals that do not sweat through their skin like humans.

The temperature of the rhinarium allows the dog to sense the warmth of other animals or objects.

This feature could play a vital role in hunting or searching scenarios, it allows the dog to distinguish between inanimate objects and potential prey or targets based on their heat signature.

Don’t know about you but aside from hunting dogs I’m thinking search and rescue dogs at this point.


Checking their Socials


Have you ever seen two dogs have a nose-to-nose sniff? Why do they do this? They’re simply using their highly developed olfactory systems to learn about each other. The moist surface of the rhinarium provides a medium that can absorb and interpret the chemical messages left behind by other dogs, including markers for identity, mood, and even health status.

They can smell how the other dogs feeling!!! How amazing is that!


Maintenance and Health


The rhinarium is not immune to health issues. Dermatitis, infections, and even tumours can affect this sensitive area of the nose. Regular checks and vet consultations are advisable for the upkeep of a dog's rhinarium if you’re concerned at all.

I tend to worry a little if the temperature of the Rhinarium is warm but keep an eye on it and has never been an issue for us.




The rhinarium is more than just a moist snout or the kissy bit of the nose; it's a sophisticated sensory organ that gives our dogs an immense amount of information about their environment and other dogs. It’s a marvel of biological engineering and an essential part of what makes a dog's nose one of the most effective natural smell detectors in the animal kingdom.




The External Nares


I thought, ‘what is that?’, I've never heard of  the 'external nares', but it’s a lot simpler than I considered. It’s the nostrils.

In dogs, these simple holes in the nose are much more than just for breathing; they’re the gateway to their amazing sense of smell. The external nares are for much more than the basics of inhalation and exhalation. They’re the gateway to a complex sequence of processes that allow dogs to perceive, understand, and respond to their surroundings in a manner that we will never fully comprehend or experience.




The external nares, or nostrils, are the two visible openings in a dog's nose that lead to the nasal cavity. These are the entry and exit points for airflow during breathing. Many breeds of dogs have the ability to control these openings to a point, to allow for more efficient sniffing and smell exploration.

Even though they look just like holes they’re far more intricate, with intricate internal flaps and structures, often referred to as alar folds (more on this later).





Dogs possess up to 300 million olfactory receptors, or smell detectors, compared to a human's 5 million. Let me break that down, we have 1.67% the smelling capability a dog has, or the dog’s olfactory capability is 5900% better than ours! That’s just mind blowing!

The nostrils are essential to and are the start of their elaborate process of scent detection. When a dog sniffs, the action air is funnelled in and directed over the moist rhinarium and then on to the olfactory epithelium.


Directional Sniffing


Have you ever seen their nostrils move in different directions, have a look. They can move their nares independently allowing them to determine the direction from where a scent is coming. By adjusting the position and opening of each nostril, they can create a sort of 'stereo surround smell' effect.

Similar to how we use our two ears to locate the source of a sound.


Respiration vs Olfaction


Do you sniff for a smell every time you breathe? Of course not, neither do dogs. When a dog sniffs, like us, the airflow pattern changes, allowing a separate path for olfaction and respiration.

This design ensures that the dog can continue to breathe while holding onto a smell as it considers what it is.


Health Considerations


The external nares, or nostrils remember can sometimes become the site for various health concerns such as allergies, foreign body obstruction, or respiratory infections.

Brachycephalic breeds like Bulldogs or Pugs may suffer from stenotic nares, a condition where the nostrils are too narrow, leading to breathing difficulties. Regular health checks and prompt vet attention can help address any issues related to the external nares.




The external nares, or nostrils, are sophisticated structures that contribute to a dog's exceptional olfactory abilities. From sniffing out drugs or explosives to detecting medical conditions like cancer, the abilities granted by these amazing structures are only beginning to be fully understood. The next time you see your dog having a good sniff on a walk, have a think about what’s going on in their head.




The Philtrum


This is the small groove that runs from the dog's upper lip to its nostril. It’s not there by accident, nothing is. It too, serves a purpose. 


It's the vertical groove, or line that runs from the top of a dog's upper lip to the rhinarium (above). It will vary in size across breeds but it’s basic form will be similar across all dogs.




The philtrum is made of the same skin and muscle tissue that makes up the rest of a dog's snout. It's not too complex, but its design is functional.




The main function of a dog's philtrum is to direct moisture from the mouth to the rhinarium. This moisture helps to keep the rhinarium wet, which, in turn, enhances a dog's smelling capabilities.

A moist rhinarium will capture scent particles from the air better, helping the dog in tracking, hunting, or simply exploring its environment.


Heat Regulation


While dogs mainly regulate their body temperature through panting, the moistening effect helped by the philtrum also helps your dog to cool down. The moisture that travels up the philtrum evaporates at the rhinarium, aiding in thermoregulation (regulating body temperature).




When dogs self-groom they often lick their noses. The philtrum serves as a natural channel for the moisture from the tongue, helping clean the sensitive rhinarium.


Social and Behaviour


While the philtrum's functions are physiological, it also has a behavioural impact. A dry philtrum can be an indicator of dehydration or ill health, indicating a trip to the vet is maybe required, often for a simple health check.

The moisture level in a dog's nose can also change due to emotional states like stress or excitement, which can affect the philtrum's role as in transporting moisture.


Health Considerations


The philtrum is generally a low-maintenance aspect of a dog’s anatomy but can be subject to skin infections, dermatitis, or injuries like cuts and abrasions. A sudden change in the appearance of the philtrum, such as redness, swelling, or dryness, should warrant a veterinary consultation to rule out any underlying health issues.




A seemingly minor bit of a dog's nose, the philtrum is an important part of the dog’s sensory experience. It enhances the dog's smelling abilities and helps in self-grooming and cooling, so the next time you find yourself looking at your dog's nose (surely it can’t be just me that does this), take a moment to think about this small groove and how it plays such a pivotal role in your dog’s life.




The Alar Fold


The alar fold is a flap of tissue located at the opening of each nostril, or external naris. It helps regulate airflow and filters out particles that could otherwise enter the nasal passages. It’s more obvious some breeds but can vary widely among individual dogs.




Made up mainly of soft tissue and cartilage, the alar fold is flexible, allowing an degree of movement, allowing our dogs to control the intake of air and various scents carried by the air.



Airflow Regulation


The alar fold helps to control and direct airflow into the nasal passages. When your dog sniffs, the alar folds can adjust to channel air more efficiently towards the olfactory receptors enhancing the dog's sense of smell.


Particle Filtration


It can filter out large particles like dust or dirt that might otherwise enter the nasal passages. This filter serves as a first line of defence against potential respiratory irritants.


Respiratory Health


By filtering and directing airflow, the alar fold acts as a safeguard for the dog's sensitive respiratory tract.


Health Considerations


The alar fold can be affected by infections, irritants, or anatomical abnormalities.

Some breeds, particularly brachycephalic dogs like Bulldogs and Pugs, can suffer from overly prominent or obstructive alar folds that can cause respiratory distress. These conditions often require a visit to your vet and in some cases require surgical alteration for the health and comfort of the dog.




To put it simply, the Alar Fold serves acts as the gatekeeper to the nasal passage.





I hope this wasn’t too boring, I’ll admit, I had to take a few breaks during this one. But at least now every time you look at your dogs nose you know what’s going on at least on the outer edges of that amazing organ.