If you haven’t already, please take the time to read the Introduction to Pheromones page.
A lot is written about pheromones on the internet, but much of the information out there is inaccurate. You can usually rely on “scientific” websites, but even they have their bad apples, some of which are displaying outdated information on pheromones or have fallen victim to the many pheromone fallacies that exist. Even worse are the plethora of junk pheromone stores which are the usual perpetrators and proliferators of the inaccuratepheromone information. Here we will be discussing exactly what a pheromone is (please note: not all of this is established science, but it is the most up to date understanding of pheromones even if it isn’t academically supported).
Definition of “PHEROMONE”
An amalgamation of the definitions of pheromones offered by www.dictionary.com is:
“A chemical secreted by an animal, usually associated with insects, which influences the behavior, physiology or development of others of the same species, often functioning as an attractant of the opposite sex.”
The word “pheromone” is derived from the Greek “pherein”, which means to carry, and hormon, which means to excite. Thus, pheromones can be described as an inter-body hormone, or a chemical that transmits a message between bodies. These messages are detected by other individuals which may or may not be of the same species, and usually signal something (be it fear, aggression, sexual arousal or many others) to those individuals. The effects of the detection of this signal carried by the pheromone or pheromones are varied and could range from sexual excitement to avoiding contact with an individual who is sending the signal. A more specific example of this is the reported altering of the phase of the menstrual cycle of women who live in close proximity, which has been linked to certain pheromones.
In mammals there are three groups of pheromones:
- Releaser pheromones that “release”, or cause, an almost immediate change in behavior. Examples of this include attraction and aggression.
- Primer pheromones have affects that are more long term, for example the altering of the phase of menstrual cycle in women.
- Information pheromones carry information about an individual. This might include fitness, immune system type (Major Histocompatibility Complex genes), etc.
Generally, the pheromones in pheromone products are hormone related. For example, androstenone, androstenol and androsterone are all androstenes, and generally signify factors involved with sex. Copulins, a group of pheromones only produced by women, are mostly acids and organic acids.
How pheromones are produced
In humans pheromones are secreted onto our skin through the apocrine glands (sometimes called human scent glands). These are similar to eccrine glands where our salty sweat comes from, but the apocrine glands secrete a more oily substance. The apocrine glands are normally associated with hairy areas such as arm pits and the crotch area, and are also usually accompanied by eccrine glands which help to disperse the pheromone secretions. Apocrine glands are activated at puberty, along with hair growth in the axillary (arm pit) regions and crotch which increase the surface area for pheromone dispersal. Certain pheromones are directly related to masculinizing or feminizing hormones (testosterone or estrogens), and so high levels of these hormones will cause high levels of the related pheromones to be released.
Pheromones evolved because metabolic waste (hormones, short peptide chains, fats, sugars, etc.) that was secreted onto an animal’s skin can give certain information about the internal chemistry and health of that individual. Over time species adapted to this fact giving rise to the whole pheromone chemical communication system. Modern animal and insect species have a somewhat more specialized pheromone system, where secretory glands and receptor systems have evolved.
Bacterial action may also have some role to play in pheromone production, but not much is known about this at the time of writing. For example, the pheromone androstenol may oxidise (by bacterial action) to androstenone. Androstadienone can also be converted into androstenone. However, bacteria are responsible for causing the bad smells associated with body odor, and they do this by metabolising the chemicals (including the pheromones) in the oily apocrine secretions. A study on bacterial action on pheromones can be found here.
Copulins are created in a different way to the “hormonal” pheromones. They are secreted into the vagina along with the bodies natural lubricant in redinness for sex.
How pheromones are sensed and processed
Pheromones fall under a category of chemical sensing (chemosensing for short) that is very similar to the way we smell. Our regular sense of smell (which is what you are using when you are smelling flowers) is called olfaction, but pheromones are thought to be detected and processed through an accessory olfactory system. In mammals this is the Vomeronasal System. This consists of vomeronasal pits situated somewhere in the nose, at the bottom of which lies the Vomeronasal Organ (VNO), which is where cells specialized for detecting pheromones lie. From here signals are sent by neurons (nerves) to the accessory olfactory bulbs, which is the part of the brain responsible for processing the information relayed by the pheromones and mediating a response. Most pheromone signals will end up at the hypothalamus. Interestingly, the epithelium of sensory cells in the nose is sometimes referred to as an extension of the brain because of their location and the way the signals are processed.
In humans, this picture of pheromone sensing becomes more complicated with some scientific studies casting some doubt over the existence of a VNO in humans, which it was thought would rule out the possibility of human pheromones having any effect on other individuals. There was also some doubt over the existence of the appropriate genes that would code for the pheromone receptor proteins in the receptor cells, making it even more likely that the pheromones being secreted onto our skin would be redundant. With this and the thoughts that our VNOs are vestigial, we are left with a situation where the whole pheromone system as an evolutionary relic akin to the appendix. Some suggest that this is due to the evolution of tri-colour vision, which led to an evolutionary trade off. However (and there had to be a “however”, or I wouldn’t be writing this!), anecdotal evidence from pheromone users has always contradicted the science in this regard, but only relatively recently has the science started to catch up with the anecdotal evidence.
First of all, (aside for anything concrete about the vestigality of the VNO in humans) there is no evidence that the VNO is actually required for pheromones to be detected, and current knowledge and speculation is leaning towards the idea that VNO is not the crucial pheromone sensing organ it was once thought to be, at least to the point of having the pheromone detection load shared with the generic olfactory membranes (click here for relevant study). There has also been significant evidence for the detection of pheromones having an impact on brain activity of specific areas of the brain (click here for relevant study), which has actually shown that the presence of that particular pheromone affects activity in parts of the brain linked with social cognition and attention. Incidently, while our organs of chemosensing in general have reduced in size, the areas of the brain associated with the processing of these signals have actualy grown in size compared to other areas. There is also evidence (click here for relevant study) that pheromones affect the release of Luteinizing Hormone which itself is responsible for causing temporary spikes in the release of sex hormones (specifically testosterone), which can happen during attraction and arousal.
Interestingly, the most abundant pheromone on the market is androstenone, but this pheromone has been shown to have no action in the VNO. The only male pheromone on the market that has shown to have an effect on the VNO is androstadienone, which is a less well known male pheromone. We are therefore left with two categories of pheromone, compounds that activate the VNO and those that don’t. The first type can be subcategorised into a group called vomeropherins, but normally all of the compounds are just labeled “pheromones”.
Contrary to popular belief, pheromones do have a perceivable odor that we can detect through normal olfactory pathways. This smell is mostly identified as an acrid bad body odor smell, but some pheromones have a more pleasant smell and some have been described as the scent of fresh sweat, in a good way. However, these smells are only detectable at high concentrations. The “pheromones are completely odorless” myth arose due to the fact that some of the action of pheromones which causes reactions in other people is subconscious, and the pheromones can be present in levels far lower than their detection thresholds for generic olfaction to have an affect. This means that pheromones do not have to be smelt to work. There are also those who can not actually smell androstenone (about 25% of the male population), although studies suggest that people’s noses can learn to smell androstenone (relevent study).
The affects of pheromones on behavior gets even more complicated in humans because we have evolved higher processing (consciousness) which can override, contradict or otherwise alter the affects our basic instincts have on our behavior. Take, for example, a situation where a guy is in a deeply committed relationship and is exposed to a very attractive signature of female pheromones. Here, higher processing would at the very least (assuming a high level of integrity on the guy’s behalf) cause the attraction to be ignored, and at the most could cause the guy not to notice the woman at all. Behavioral reactions to pheromones have another added layer of complexity due to the nature of attraction and courtship in humans, with factors such as social status (think about levels of “attainability” here) and shyness playing their part to inhibit pheromone influences, but there are other factors such as a persons tendency to be sexually aggressive or just aggressive in general that can amplify the normal pheromone effects. A persons mood prior to sensing the pheromones can also play a role. All of these factors are intensified with the use of exogenous (i.e. from a bottle) pheromones.
General pheromone discussion
The whole concept of using exogenous pheromones relies on there existing a kind of “human musk”, similar to the musk in deer. This musk would consist of many different pheromone compounds, each or by association with other pheromones carrying a message. Some of these messages are used as criteria in attraction; an example of this would be testosterone levels in men. Several compounds may contribute to this message being transmitted, and some will signal “high testosterone” if they are secreted in high levels on the skin. These compounds or compound could then be identified and synthesized. However, the pheromones that are sold as pheromone products are only gross attraction pheromones, meaning that they only signal “high testosterone” or “youth” or “approachability” to everyone, and don’t give any information about the person behind these particular criteria. There is further evidence which suggests the existence of a very specific pheromone profile, but it will be made up of other compounds, probably relating to the immune system (opposite MHC genes, the “sweaty t-shirt study”, and this article) and other genetic qualities. It would therefore be possible to tailor a pheromone mix specifically for an individual, in essence creating the impression of an ideal partner, but at the moment this is beyond current technology.
The pheromone compounds that are commonly used in pheromone products are:
There are others, but these are the most common three. Click here for details on some of the general affects of these pheromones.
So, pheromones are not miracle sex attractants, but they do play a role in the day to day interactions of humans, albeit a more subtle one. They are a part of everyone’s life; they say that only 10% of communication is verbal, but how much is pheromonal? More than you think maybe.