While the effects of pheromones on humans are less obvious than in other mammals, they still strongly affect our behavior.
Many pheromones are air borne particles that pass through air after evaporation by the heat of the body.
Some pheromones are heavy proteins that cannot be passed through the air by evaporation.
These are passed by physical contact such as by kissing or skin-to-skin contact.
Kissing occurs in all human cultures and is a way of passing identification pheromones.
When a mother kisses her baby, this increases the mother-baby bonding.
Pheromones activate pre-coded genetic programs.
They increase production of GnRH (Gonadotropin Releasing Hormone) that starts the pulses and cycles of sex hormones which govern sexual development.
GnRH also affects activity in the brain that affects sexual development and behavior.
Pheromones act in two ways. The first is "signal pheromones" that cause others to become aware of your presence and cause immediate changes in behavior by activating certain areas of the brain.
The second class is "priming pheromones" which trigger increases in GnRH production and which often require kissing or skin-to-skin contact.
This, in turn, increases production of many hormones that affect development, metabolism, and mating behavior.
Often, fertile women have difficulty becoming pregnant. In married couples, it takes, on average, six months of sexual intercourse to produce the first pregnancy.
One theory is that the woman's body is slowly adjusting to her husband's pheromones before becoming receptive to pregnancy.
Newborn infants follow the breast odors emanating from their mother's nipple/areola region.
These odors exert a pheromone effect that guides the infant to nurse at their nipples1. Within minutes after birth, the mother's breast odors cause a head turning of the baby for the nipple and helps guide the baby to successful sucking for milk.
Newborns soon learn to recognize their own mother's unique odor signature which builds mother-infant attachment.
Nipple pheromones also may explain a lot of behavior in young men. The irrational obsession of men with women's breasts has long been a puzzle.
It may be that this is a natural bonding pheromone that men require for their emotional stability and helps tie them to women.
Women often call men pigs (or vertical pigs). On the other hand, men very rarely use this term when talking about women.
Since the domestication of wild pigs 7,000 years ago, women have intuitively known that many male human hormones are very similar to those of pigs.
The key pheromone in pigs is androstenone, which gives the characteristic odor to urine from boars (male pig) and some of the odor to human male urine also.
Female pigs are extremely aware of the smell of androstenone as are human female to male smells.
Pig breeders spray androstenone from aerosol cans on the backs of female pigs to determine whether the female is ready for breeding - if the sow arches her back, she is sexually receptive.
A lack of smell limits emotional attachment. Approximately 1.3% of people are born with a total lack of smell or Anosmia.
And most of us lack the ability to smell certain fragrances.
A study found 5 to 8% of students at Oxford University could not smell freesia, a very fragrant flower.
Persons with Anosmia often complain about a lack of libido.
While they may marry, behavior that is emotionally distant remains a problem. Some researchers have noted that the decline in sex drive with aging coincides with the decline in smell.
One answer to reduction in the ability of smelling as we get older is to increase our pheromone signal with essential oils and pheromones.
In goats, sheep, and pigs, male dominance in competition for females is determined by the strength of the male's pheromone - and not physical strength or beauty.
The animals with the strongest pheromones have more confident threat displays without giving signals of fear.
This reduces the incidence of actual physical combat for females - especially among deer and moose.
The pheromones of the male with the strongest pheromone causes a psychological castration of other males which helps remove them from competition.
In pigs, the pheromone androstenone triggers the female's receptivity to the male.
This type of pheromone dominance may also apply to humans since many researchers think human pheromone responses are very similar to pigs (Hard on our ego but probably true).
Truffles, which are a fungus that grows underground near oak trees in France and Italy, are highly valued as human aphrodisiacs.
Pigs also are passionately attracted to truffles and are used to locate the truffles.
So if you are a man, your pheromone smell may affect females more strongly than your good looks, money, or wit.