EndocrinologyWritten by Christian NordqvistLast updated: Thu 14 Apr 2016A pheromone is a chemical an animal produces which changes the behavior of another animal of the same species (animals include insects).
Some describe pheromones as behavior-altering agents. Many people do not know that pheromones trigger other behaviors in the animal of the same species, apart from sexual behavior.
Pheromones, unlike most other hormones are ectohormones – they act outside the body of the individual that is secreting them – they impact a behavior on another individual. Hormones usually only affect the individual that is secreting them.
This article will take a brief look at pheromones and whether they can be found in humans.
Fast facts on pheromones
Here are some key points about pheromones. More detail and supporting information is in the main article.
Pheromones are similar to hormones but work outside of the body
Pheromones induce activity in other individuals, such as sexual arousal
The McClintock effect refers to women’s menstrual cycles combining, perhaps in response to pheromones
Some chemicals have been investigated for pheromone actions in humans but evidence is weak
Virtually all insects use pheromones to communicate
Most alleged pheromone products that can be purchased online are ineffective
Gustav Jäger was the first to propose the idea of pheromones – he called them anthropines
There are four types of pheromone: releaser, primer, signaler and modulator.
What do pheromones do?
[Man sniffing armpit]
Pheromones are widely utilized throughout the animal population.
Pheromones can be secreted to trigger many types of behaviors, including:
To follow a food trail
To tell other female insects to lay their eggs elsewhere (epideictic pheromones)
To respect a territory
To bond (mother-baby)
To back off.
It is believed that the first pheromone was identified in 1953. Bombykol is secreted by female moths and is designed to attract males. The pheromone signal can travel enormous distances, even at low concentrations.
Experts say that the pheromone system of insects is much easier to understand than that of mammals, which do not have simple stereotyped insect behavior.
It is believed that mammals detect pheromones through an organ in the nose called the VNO (Vomeronasal Organ), or Jacobson’s organ, and connects to the hypothalamus in the brain.
The VNO in humans consists of just pits that probably do not do anything; interestingly the VNO is clearly present in the fetus but atrophies before birth. If humans do respond to hormones, most likely they use their normal olfactory system.
Pheromones are commonly used in insect control. They can be used as bait to attract males into a trap, prevent them from mating, or to disorient them.
Do humans have pheromones?
According to thousands of websites that promise sexual conquests if you buy their pills, human pheromones exist – bear in mind that their aim is to get you to buy their products. However, most proper, well-controlled scientific studies have failed to show any compelling evidence.
[Woman sniffing armpit]
Some believe that androstenone acts as a human pheromone.
Gustav Jäger (1832-1917), a German doctor and hygienist is thought to be the first scientist to put forward the idea of human pheromones. He called them anthropines and said that they were lipophilic compounds associated with skin and follicles that mark the individual signature of human odors. Lipophilic compounds are those that tend to combine with, or are capable of dissolving in lipids.
Researchers at the University of Chicago claimed that they managed to link the synchronization of women’s menstrual cycles to unconscious odor cues. The head researcher was called Martha McClintock, hence the coined term “the McClintock effect.”
When exposing a group of women to a whiff of sweat from other women, their menstrual cycles either accelerated or slowed down, depending on when during the menstrual cycle the sweat was collected – before, during or after ovulation.
The scientists said that the pheromone collected before ovulation shortened the ovarian cycle, while the pheromone collected during ovulation lengthened it. Even so, recent analyses of McClintock’s study and methodology have questioned its validity.
Recent research into pheromones
A Swedish study found that lesbians react differently to AND (progesterone derivative 4,16-androstadien-3-one) compared with heterosexual women. AND is ten times more abundant in human male sweat than female sweat.
A study, published in Respirology in January 2016, showed that AND caused swelling in the erectile tissue of female noses. This was taken as evidence that AND might be a functioning pheromone.1
Another contender for the role of human pheromone is androstadienone. There is some evidence that androstadienone, a component of male sweat, increases attraction, affects mood and cortisol levels and activates brain areas linked to social cognition. One study found that androstadienone increased cooperative behavior in males.2
Androstenone, secreted only by males, has also been tested for its potential role as a pheromone. According to some studies, androstenone increases a woman’s mood, especially if she is presented with it close to the time of ovulation.3
Overall, evidence for the existence of pheromones in humans is weak but it can not be ruled out entirely. If human pheromones are ever found, the likelihood is that their effects are incredibly subtle.
Types of pheromone
There are four principal kinds of pheromones:
Releaser pheromones – they elicit an immediate response, the response is rapid and reliable. They are usually linked to sexual attraction.
Primer pheromones – these take longer to get a response. They can, for example, influence the development or reproduction physiology, including menstrual cycles in females, puberty, and the success or failure of pregnancy. They can alter hormone levels. In some mammals, scientists found that females who had become pregnant and were exposed to primer pheromones from another male, could spontaneously abort the fetus.
Signaler pheromones – these provide information. They may help the mother to recognize her newborn by scent (fathers cannot usually do this). Signaler pheromones give out our genetic odor print.
Modulator pheromones – they can either alter or synchronize bodily functions. Usually found in sweat. In animal experiments, scientists found that when placed on the upper lip of females, they became less tense and more relaxed. Modulator hormones may also affect a female’s monthly cycle.