In response to emotional stress and sexual stimulation, apocrine glands release secretions through hair follicles. The human stress response may therefore result in the production or intensification of one s natural body odor which is detectable to a nearby animal. Thus, if a person becomes fearful in the presence of an animal, that animal may be able to detect a new odor, and may therefore be alerted to the person s presence. Additionally, it is unlikely that such an olfactory cue acts alone to incite aggression in the animal. Certain non-human animals may also produce a scent as a result of fear or emotional stress.
Many mammalian species deposit various odors when they are alarmed.
For animals which typically scent mark objects, such as cats and dogs, odors produced as a result of emotional stress are not usually deposited at a specific marking spot. Chemical signals produced under stress, however, are thought to function in alerting conspecifics of danger, rather than in eliciting aggression in an intruder. Therefore, taken literally, the smell of fear might be more appropriately termed the smell of danger, and may function as a warning to others after danger has been encountered, rather than being the cause of a dangerous encounter. The use of pheromones to alert conspecifics or members of a social group to the presence of an intruder or a potential attacker is common in many animal species. In this manner, the fear scent produced by a honeybee worker does not provoke aggression by a predator, but instead functions in hive protection.