You may have heard that some animals, such as bees and dogs, can smell fear. That statement is somewhat true and somewhat misleading, according to Penn State University. Fear itself does not have a scent, but the pheromones produced when an animal is afraid do.
Pheromones are chemicals emitted by all animals in bodily fluids, such as sweat and urine, that send signals to other animals of the same species. They may indicate territory, aggression or an interest in reproduction. But we don’t smell these scents in the same way we would smell a fresh-baked apple pie or a fire burning in the fireplace. We detect those through our main olfactory system, but pheromones are registered through our accessory olfactory systems. PSU explains:
Communication in this system begins in the vomeronasal organ, which is located above the soft palate of the mouth, on the floor of the nasal cavity. Highly specific smell molecules detected by this organ are transmitted to the accessory olfactory bulb where they are collected and processed. Nerves from both the accessory and the main olfactory bulbs project to the limbic system, the part of the brain that deals with emotional perception and response.