We all know that dogs have a very keen sense of smell - but did you know that dogs are able to smell certain medical conditions?

With about 220 million scent receptors, compared to the 5 million in humans, dogs can smell things that are indiscernible to us. There are dogs who have sniffed out medical conditions that even doctors weren’t able to detect.

So which medical conditions are dogs able to smell? Read on to find out.


The CanadaFree Press reports a woman whose dog kept sniffing a mole on her thigh. The dog ignored all others on her body, but kept obsessing over that specific mole. The woman consulted her doctor, and the diagnosis confirmed a malignant melanoma.

This is one of many stories of dogs being able to detect cancer in their owners. It will still be a while before dogs are used by doctors to sniff out cancer in patients, as researchers still don’t know exactly what compounds dogs are sensing.

Let’s hope that this will happen in the future!


Narcolepsy is a brain disorder that affects the ability to control sleep-wake cycles, which means that a sufferer can suddenly fall asleep mid-task. This is a very dangerous condition, as someone who suffers from Narcolepsy can potentially fall asleep while driving or injure themselves during an episode.

Dogs are able to detect when an attack is coming on due to a scent that is excreted by the human body.

Mary McNeight, Service Dog Academy director tells Sleep Review: “It’s a biochemical change in the body. We do not know what the particular odor smells like due to the difference between human scent perception and dog scent perception.”


Migraine service dogs are able to hone in on the scent of serotonin, a chemical that escalates when the body is about to experience a migraine.

“By alerting to the danger long before their handlers might feel any symptoms, these dogs can warn them to take preventative medication. When Rally looks up at me and whines, I know I have about two hours before the migraine strikes, and if I can take my medication early enough, I might be able to avoid the stroke-like symptoms and incapacitating pain,” says Kendall Winship, a migraine sufferer with a service dog.

Low blood sugar

Service dogs are able to detect and alert handlers to changes in blood sugar levels.

“The dogs are trained on a scent collected from a diabetic's breath or sweat when they are experiencing hypoglycemia,” says Ralph Hendrix, executive director of Dogs4Diabetics.

The dogs can even discriminate between the scent from a previous episode, and the scent of a current one. This means that handlers can be alerted early enough to take the insulin they require.


The level of accuracy of dogs being able to detect the onset of a seizure remains questionable. Dogs may not be always be able to predict seizures, but they can certainly be trained to assist a handler when a seizure occurs.

There have been instances of service dogs learning the ability to predict a seizure. Jennifer Arnold, founder of Canine Assistants in Georgia reported that about 9 out of 10 of the service dogs her organisation has placed develop the ability on their own within a year of placement. Further research is needed to uncover more about this, however.

Fear and stress

The age-old notion that dogs can smell fear is an accurate one. Dogs can smell when we are feeling fear or are experiencing an increased level of stress, even if we aren't showing outward signs. What dogs are smelling is the surge of hormones our bodies release to respond to stressful situations, including adrenalin and cortisol.

This can be used to our benefit, as dogs can alert handlers to prevent panic attacks and other post-traumatic stress disorders.

For more information about this, read here.

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