Fear
"Can animals really smell fear?
Sharon Lynn
…For example, in humans, the autonomic nervous system is responsible for enacting a stress response. This response is thought to function in preparing the body for immediate protective action. Characteristic physiological changes comprising the fear response in humans include (1) an increased hear rate, (2) an increase in blood supply to the muscles and to the brain, (3) release of glucose into the bloodstream, (4) dilation of the pupils, (5) increased breathing rate, and (6) an increase in sweat gland activity (Janis et al., 1983). In particular, the increase in sweat gland activity which accompanies a stress response in humans may contribute to an olfactory �fear� signal.
The human body has two types of sweat glands. The first is the eccrine, or sudoriferous, gland, which is a coiled structure responsible for the regulation of body temperature through evaporation of sweat from the body surface. The second type of sweat gland is called the apocrine gland. Apocrine glands are localized to specific areas of the body with the highest concentrations occurring in the region of the axillary organs (armpits) and the groin area (Stoddart, 1990).
In response to emotional stress and sexual stimulation, apocrine glands release secretions through hair follicles. The secretions contain cellular material that is broken down by bacteria, and thus body odor is produced (Memmler et al., 1992). 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. Thompson (1988) suggests that human thermoregulatory responses to stress or fear may provide a valid measure of the intensity of emotion, but do not provide much specific information about which emotion an individual is experiencing. 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. it is, however, unlikely that such an olfactory cue provides the animal with enough information to detect that the person is fearful. Additionally, it is unlikely that such an olfactory cue acts alone to incite aggression in the animal…
Many police departments and search-and rescue squads use trained dogs to track both suspects and victims through olfactory cues. Usually, the dog is presented with an item on which the object of a search�s odor may be detected, and the dog then follows a scent trail which will presumably lead to the person. The role of a possible �fear scent� in directing a trained dog to a suspect is not well documented. One contributor to the K-9 Academy for Law Enforcement Trainer�s Resource Centers Web page suggests that, �If you want to train your canine to pick out all the people who are afraid, you can do that . . . a guilty persons odor is coming out like a smoke bomb and smells of �fear�.� However, evidence which supports this claim remains anecdotal1,2, as systematic study in this area is difficult. Nonetheless, Sigma Pseudochemicals does offer vials of human �fear scent� to those purchasers who are interested.
In the strictest sense, it is doubtful that animals can smell fear. Some animals have been documented to release a scent in response to stress. Such a �fear scent� may play some role in alerting a potential attacker. However, it is more likely that an animal will become aggressive towards a fearful individual as a result of a combination of multiple sensory and behavioral cues. While odor may play a significant role in attack behaviors among animals, olfactory cues probably do not function alone to incite aggression in mammals…"