Even the most enthusiastic dog lovers can't help but turn their noses up when their pet comes in from the rain.
The 'wet dog' smell is instantly recognisable, but why do the animals smell so bad - even after they've been washed?
Chemists from the American Chemical Society have revealed this is due to the microorganisms that live in dog fur - and they show just why dog food is so offensive to our noses.
The video begins by explaining that the nose of a canine is highly sensitive, with around 220,000,000 olfactory sensors. These sensors are so advanced they have been linked with being able to detect disease in humans
The video, the latest in the Reactions series, begins by explaining the nose of a canine is highly sensitive and sophisticated, with around 220,000,000 olfactory sensors.
These sensors are so advanced they have been linked with being able to detect disease in humans, and find explosives.
Earlier this year, for example, tests found dogs can sniff out prostate cancer with 98 per cent reliability.
DOGS CAN SNIFF OUT CANCER
Dogs can sniff out prostate cancer with 98 per cent reliability, a new study has shown.
The research, carried out in Milan, backs up tests carried out by the charity Medical Detection Dogs.
Its co-founder Dr Claire Guest said the charity's research found a 93 per cent reliability rate when detecting both prostate and bladder cancer.
She hailed the new study, describing the findings as 'spectacular'.
The latest research, by the Department of Urology at the Humanitas Clinical and Research Centre in Milan, involved two dogs sniffing the urine of 900 men - 360 with prostate cancer and 540 without.
Scientists found that dog one got it right in 98.7 per cent of cases, while for dog two this was 97.6 per cent .
They said dogs are able to detect specific volatile organic compounds in the urine but said an important question remains of how a dog would find it in daily practice.
Dogs are capable of doing this by detecting specific volatile organic compounds in the urine caused by prostate cancer.
Elsewhere, when dogs get hot they don’t sweat like humans, instead they have glands on the bottom of their paws and their noses to keep their body temperature regulated.
But the mucus on a dog’s nose additionally helps it sift through and process smells.
'When a dog smells something, molecules enter its olfactory systems and binds to the receptor cells that sends a signal to the brain,' said the video.
'Nose mucus slows down or speeds up specific types of molecules helping a dog’s olfactory system process and identify smells more efficiently.'
The wet dog smell in particular is from the microorganisms that live in dog fur, including yeast and bacteria.
The video continued that these organisms excrete 'stinky volatile compounds' but added that if these compounds are always being produced in a pet, why does the bath make them stand out?
'When a dog gets wet, the water displaces and liberates these organic volatile molecules from the surface of the dogs fur, allowing them to find their way right into your nose,' the chemists said.
Another smell that also offends dog owners is kibble.
'Kibble is made of animal fats, vitamins and minerals all held together with soy or wheat grain,' said the video.
'Dogs aren’t big-time grain lovers so experts were called in to try to attract them to the food - and it turns out the best way to make dogs eat something is to make it smell disgusting.'
For example, dogs are attracted to smells like putriscine and cadaverine - molecules that forensic scientists dub ‘dead body smell.’
A video released last year by the same society also explained why dogs like to sniff each other's rear ends.
Earlier this year, for example, tests found dogs can sniff out prostate cancer with 98 per cent reliability.The research, carried out in Milan, backs up tests carried out by the charity Medical Detection Dogs. They are also used to find explosives by police forces in the US
In 1975, Dr George Preti of the Monell Chemical Senses Centre in Philadelphia examined the anal secretions of dogs and wild coyotes to study this behaviour.
They found that on the rear-end of the dog is an area called the anal sac, which excretes identifying chemicals to other dogs.
One of the glands here is the apocrine gland, which gives the dog its natural smell.
Another called the sebaceous gland also plays a part, which mostly lubricates and waterproofs the skin and hair of mammals.
Dr Preti found that the primary chemical compounds are released from these glands, and produce a dog’s aroma, are a variety of short-chain acids and something known as trimethylamine.
Trimethylamine is an organic compound that is a product of the decomposition of plants and animals, and is the odour often associated with rotting fish or bad breath.
The wet dog smell is caused by microorganisms that live in dog fur, including yeast and bacteria. The video said these organisms excrete 'stinky volatile compounds' and when a dog gets wet, the water displaces and liberates these organic volatile molecules from the surface of the dogs fur to their owner's nose
Another smell that offends dog owners is kibble. Kibble is made of animal fats, vitamins and minerals held together with grain. To make dogs eat grain the food needs to smell 'disgusting' and this is because dogs are are attracted to smells like putriscine and cadaverine (shown) - molecules that create the ‘dead body smell’
The aroma given off by the dog is dependent upon some of the factors mentioned earlier - diet, gender, emotional state and more.
When one dog smells another, it is able to pick up on these finer details and learn information that would otherwise be mostly unavailable.
‘You’d think the smell of dog poop would overpower Rover’s sensitive smell, but dogs have a second olfactory system in their hyper-sensitive nose called the jacobson’s organ,’ the narrator explained.
This organ is designed specifically for chemical communication and not for smelling other aromas.
With its own set of nerves to the brain, the organ is able to circumvent other organs in the nose used for smelling and let the dog know the chemical characteristics of the dog it is smelling.
And so, as the video concludes, the reason dogs smell one another isn’t for fun but rather they are ‘getting to know each other in a special aromatic way.’
