and then there are very good boys

like these dogs here. They're searching for a scent

that no human can detect:

the scent of an epileptic seizure.

We've long known that dogs can detect seizures in humans

in some cases 45 minutes before they occur.

That's one reason why organizations like Handi'chiens

in France provide service dogs for people with epilepsy.

And in some cases, this can prove lifesaving.

It might give people time to take medication

that could prevent or reduce the severity of a seizure

or move somewhere safer where an injury

is less likely to occur.

Incredible?

Yes.

But proven?

Not until French researchers teamed up with Medical Mutts,

a US-based organization that trains seizure alert dogs.

That marker, they believed, was a scent

that dogs can detect.

So in 2018, they set up an experiment.

First, they collected dozen of samples of

breath and sweat from people with

different forms of epilepsy.

Some of them were taken during or right after a seizure,

while others were collected after exercise or at rest.

Then they distributed them among seven different

steel containers in this room.

Finally, they let out, or, they let in the dogs.

One by one, Casey, Dodger, Lana, Zoey, and Roo

walked into the room.

They were trained to stop and stand still

if they think they detected the scent of a seizure.

And if they were right, they got a treat,

good dog!

To the researchers' excitement, the canines excelled.

Three of the dogs, Casey, Dodger, and Zoey,

sniffed out the odor associated with seizure with

100% accuracy.

The two other pups, Lana and Roo, who had less

time to train, weren't quite as accurate.

But they still correctly identified two-thirds

of the seizure samples on their first try.

What makes these results even more remarkable

is that the scent samples were from different people

and also produced by different kinds of seizures.

And what exactly is that marker made of?

Here's the thing: We still don't know.

It's likely that seizures trigger a change in the body's

electrical activity, the researchers say.

And those changes can affect the

composition of odor molecules that

we emit through our sweat, breath, and, likely, urine.

Now, whether people emit these odors

before a seizure in time to reduce its worst effects

is still in question,

and it's not something that the researchers tested.

But some experts claim that people emit a specific

group of odor chemicals 15 to 45 minutes prior to seizing,

which dogs can detect.

So what exactly makes canines such smell superstars?

It's their incredible noses.

With as many as 300 million olfactory receptors,

a dog's nose is up to 100 thousand times

stronger than our own.

That means they can detect a few scent molecules

among trillions of them.

Scientists are now trying to build electronic noses

that are just as powerful.

The idea is that they too

could be used to sniff out diseases.

But for now e-noses are nowhere near as good as dogs,

and in some ways, doesn't that seem like a good thing?