You’re in a dark alley way. You notice a wild dog barking and growling at you.  You’re afraid, very afraid. A bead of sweat rolls down your cheek. Just look calm, you think. Then you remember that dogs can smell fear. With one sniff this dog will know that you are terrified, and no amount of looking calm will save you. More sweat appears on your forehead. It’s at this point you think, What if it’s just a myth? What if dogs don’t actually smell fear? Your eyes narrow, looking straight at this puppy. You open your bag and whip out this book. With eye fixed on the dog and another eye on this page, you find out for yourself if dogs, scientifically speaking, can smell fear.

The myth about dogs and their smelling abilities says that if you are afraid, a dog can smell it. It’s as simple as that really. Fear-smelling is a handy ability to have. If you can tell that another animal is scared, they become an easy target. Plus, when animals and humans are incredibly afraid, they can even freeze with fear. For example, studies of mice and rats have shown that these rodents freeze up when they smell strong cat odours. If a dog can take one look at a lilly-livered old rat, and know that he is frozen with fear, that’s dinner on the table before you can say “the only thing to fear is fear itself.” But is it true? Could Inspector Rex really be that clever?

For dogs to be able to smell fear it would mean that animals, including humans, have to make a fear smelling substance. Many animals, from ants to mice to cats, use smells to communicate with their animal buddies and fend off attackers. Weasels and skunks, for example, let out a horrible odour from their anal glands (also called a fart) when foreign intruders are around. Domestic and wild cats do the same. These smells, called alarm pheromones, ward off attackers (and any other creature that has the ability to smell). Alarm pheromones also alert other skunks to the threat to danger. In a bee hive, if a bee detects a foreign odour they will release alarm pheromones, which act like a ‘call to arms.” Bees near the hive will quickly fly to the hive, ready to fight the intruder. If bees, cats and skunks can create fear smelling odours, can humans?

The most recent and relevant study performed on the topic was done in 2002 by the University of Vienna. The researchers placed pads under the arms of females and made them watch a scary movie, Candyman, and a not-so-scary movie, Lokorama. Candyman follows the story of a serial killing clown, while Lokorama follows the journey of a train, as it calmly moves down a track. The researchers removed the pads and asked other females if they could smell a difference (the pads were unlabeled). The females were also asked to describe the smells using a multiple choice questionnaire, which included descriptions like: does it smell like sex, aggression, or fear? The researchers found that the females, for the most part, could tell the difference between the smells. Sweat from the horror film was described as stronger, more unpleasant, and more aggressive than the neutral film sweat. This tells us that we do release different smells in different environments, and that these differences can be detected by other people. But could dogs detect it?

The study didn’t venture into the canine, and no study has gone on to see if dogs react differently to the different smell. But considering that dogs have a particularly strong sense of smell, much stronger than humans, (think of drug searches) it seems that if humans can smell the difference, a dog could too.

It’s also possible that humans don’t actually have a fear scent specifically (after all, it was only one study) but we just release regular sweat when we are scared and dogs can smell it. Many studies show that when humans are afraid we sweat more. This is because our body prepares us to run away from danger, and sweat will allow us to release body heat that will build up as soon as we start to sprint. The strong smell of sweat might be what a dog detects.

Another explanation to the canine myth is that when people say dogs can “smell fear” they got their grammar wrong. Perhaps dog’s sense fears from our behaviour, and don’t smell scents of fear? Maybe they just recognise certain movements, such as backing away, and they know you’re afraid. If this is the case, their sense of fear has nothing to do with smelling skills., which is quite a disappointment.

If a grammatical error is to blame for the myth that dog’s can smell fear that takes the fun out of the whole discussion. In an instant Lassy, Bingo and Inspector Rex have been demoted from creatures with superpowers of smelling deduction, to animals, just like us, that know someone is afraid because of behaviour! No longer are we hostage to their ‘mind reading’ snouts. But, perhaps, like the bee, and the skunk, we also release pheromones of fear that dogs can smell. Only time (and a couple more studies) will tell us if dogs really can smell human fear.

What to do if you meet a growling dog in an alley way

• There are many different reasons that a dog may be aggressive. One is fear-induced aggression, where the dog will be aggressive because they are actually afraid of you. A study in 2005 found that if a person approached a dog aggressively, it was more likely respond with antagonistically than if you weren’t forceful. So don’t try to fight fire with fire, and don’t be hostile toward the canine.