Can Dogs Smell Fear?

Some urban legends say dogs are able to smell fear in people, so that if someone is afraid of dogs and stands in front of one, it can smell that fear. There's some truth and some fiction in this kind of urban legend — let's see whether they can actually smell it or not.

Pheromones

Even without realizing it, humans release different pheromones depending on our state. So if we're happy, we give off certain pheromones, very different from the ones we release when we're scared.

Dogs' highly developed sense of smell can detect these pheromones, so they can tell how we're feeling based on our own body's chemical reactions.

Heartbeat

An upset or scared person has a much higher heart rate than a relaxed person. This is due to the adrenaline our body releases when it finds itself, or believes it finds itself, in a dangerous situation.

Dogs' hearing is also highly developed, and they're able to hear our heartbeat, especially when it's more intense.

Sweat

Another sign of a nervous or scared person is the sweat they give off, which dogs can obviously smell too.

Restlessness and Agitation

A scared person will usually appear very restless and agitated — another sign that, combined with the ones above, will give away their emotions to a dog.

Conclusion

Dogs can't smell fear itself, but they can detect when a person is feeling afraid based on the changes their own body produces: pheromones, faster heart rate, sweat, or restlessness.