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Dog’s Sense of Smell: What Dogs Learn From Scent

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dogs sense of smell blog graphic with picture of dog sniffing man's nose

Have you noticed how thoroughly your dog sniffs you when you return home after being away? With a dog’s sense of smell (10,000 to 100,000 times keener than humans), he can determine our mood, or if we’re ill.

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What Information Dogs Gather From Scent

According to an article in the Spring 2020 issue of Modern Dog Magazine, research has determined dogs can learn a person’s mood purely by scent. When we’re in a good mood, we emit pheromones, a sign of good mood.

You’ve probably read stories of dog’s that have signalled a sign of illness in their human when tests have not detected disease. The disease causes a change in body chemistry that causes a change in scent that is detectable by dogs.

The Story of George The Standard Schnauzer

One documented case involved George, a standard Schnauzer. George was trained to detect the presence of melanoma in humans. He gave indication melanoma was present with a patient, even though the mole George found on the patient had been examined by three different doctors, and biopsied twice.

Doctors removed the mole, did a cell-by-cell examination and found Stage 2 melanoma. George helped save the patient’s life!

Why Dog’s Sense of Smell Is So Keen

Dogs are able to pick up these signals with the presence of Jacobson’s organ, located in the bottom of dog’s nasal passage. Humans don’t have this organ, accounting for a less powerful sense of smell for us.

Dogs can also tell if we’re nervous. Our body often begins to perspire, and dogs pick up the perspiration scent.

Some researchers and trainers theorize that a dog’s affection for us helps refine the sense of smell. The theory is that dogs have fun when doing scent work.

if they detect a difference in scent for some reason, dogs worry the fun will stop, so they’re looking out for us, and ultimately looking out for themselves by keeping us well.

Scents That Repel Dogs

Because dog’s sense of smell is so keen, there are scents they tend to avoid;  Scents most dogs tend to avoid include:

  • Vinegar
  • Citrus
  • Mothballs
  • Rubbing Alcohol
  • Cayenne Pepper
  • Pipe Tobacco
  • Coffee Grounds
  • Essential Oils (mustard oil, citronella oil, lemon grass oil (not safe for dogs), eucalyptus oil (not safe for dogs)

If you’re trying to keep your dog off a particular piece of furniture, spray a bitter or citrus-based spray that’s safe for fabric on your finger. Offer the sprayed finger to your dog to sniff, if he backs away that scent should work as a deterrent. If he doesn’t back away, try another citrus based scent. Ensure the product you pick indicates it’s human and pet safe before using. If you have questions about a product, check with your vet before using.


After taking a walk with your dog, notice how your house smells when you return. Does it have a strong citrus scent?  Since many dogs aren’t fond of citrus scents, avoid those as much as possible.

Think of how a strong perfume can be an assault on our senses. Since a dog’s sense of smell is much stronger than ours, even a small amount of a scent that bothers him will be very unpleasant.