Background: What Pheromones Are & How They Work
  • What Are Pheromones?

    Pheromones are aromatic compounds which, by way of the olfactory system, exert an effect on the thought, feeling, perception, behavior, or endocrine functioning of the wearer and those around them. The use of pheromones to signal alarm, food trails, and sex among insects has been particularly well documented. In addition, some vertebrates and plants have been shown to communicate by using pheromones.

    It is important to distinguish between the term pheromone as it is used by biologists, which generally implies species-specificity and a direct causal impact on behavior, and the manner in which it is used by experimental enthusiasts. In the context of this site, pheromone may refer to any aromatic compound which influences those exposed to think, feel, or behave in noticeably different ways.

    Are Human Pheromones Real?

    The issue of human pheromones remains controversial. Many scientists continue to believe that humans do not respond to olfactory signals in the same way that insects and animals do. These arguments are presented in the recent book The Great Pheromone Myth by Richard Doty. However, there is some good experimental evidence for pheromonal influence between humans.

    The best-known case involves the synchronization of menstrual cycles among women based on unconscious odor cues (the McClintock effect, named after the primary investigator, Martha McClintock, of the University of Chicago). This study exposed a group of women to a whiff of perspiration from other women. It was found that it caused their menstrual cycles to speed up or slow down depending on the time in the month the sweat was collected: before, during, or after ovulation. Therefore, this study proposed that there are two types of pheromone involved: "One, produced prior to ovulation, shortens the ovarian cycle; and the second, produced just at ovulation, lengthens the cycle".

    James V. Kohl published a comprehensive model of human pheromone activity in the Journal of Psychology and Human Sexuality. He has reported study results finding that women exposed to a male wearing a pheromone mixture of androstenol and androsterone (his Scent of Eros blend) exhibit higher levels of flirtatious behavior than controls.

    Additional studies found that female humans preferred the body odor of men whose cortisol levels were higher. Testosterone and estradiol concentrations did not appear to affect this preference. More studies are referenced on the pages for individual molecules. Androstadienone is the best-studied pheromone molecule, with estratetraenol, androstenol, and androsterone being also fairly well-represented in the literature.

    Mechanism of Action

    Administration via olfaction is very different from absorption into the bloodstream. Molecules that are smelled do not absorb into the bloodstream, but rather directly stimulate nerves within the olfactory system, which in turn act upon the hypothalamus and the orbital prefrontal cortex. Here's a really good synopsis of the structure of olfaction:

    Because of the specificity of this mechanism, a GABAergic pheromone such as androstenol cannot be thought to act generally the way a GABAergic drug like valium would. Rather, it exerts influence on a particular subset of low-level neuroendocrine and cognitive processing functions. The overall effect should be one of modulation -- of shaping perception and interpretation to make subjects more prone to a particular quality of experience. In most cases, the experience that is shaped is the experience of the pheromone wearer -- which is to say, a particular type of social impression is produced.

    Gender-specific pathways have also been identified in the processing of specific pheromone molecules. Men exposed to estratetraenol exhibit hypothalamic activation, while women exposed to this chemosignal exhibit activation of the amygdala and piriform cortex. These gender-specific response patterns are reversed in people exposed to androstadienone.

    A substantial number of molecules have been identified which exhibit pheromone activity when applied externally in an appropriate fragrance carrier. Despite the widespread belief--incited by marketers--that pheromones are primarily sexual in nature, each pheromone molecule appears to possess unique social and emotional properties.

    How to Identify Potential Pheromones

    The number of molecules with noticeable pheromonal activity is growing all the time. The criteria by which suspicions of suitability for use as a pheromone are aroused for endogenous substances vary by investigator, but generally include:
    • Secretion in sweat, urine, or saliva
    • Known activity as a neurosteroid
    • Low molecular weight, such that free diffusion through the air would be feasible – generally below 400 g/mol

    From the known active human pheromone molecules, it is possible to develop analogs such as Erox’s ER303 (Muricin aglycone).

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