We highly evolved mammals don’t go around smelling each others' butts, but we still have the same pheromone-sensing organs our remote ancestors did.
The vomeronasal organ, located in the nasal passages, absorbs chemicals from the air and sends information to the brain, bypassing the cerebral cortex (the executive brain) and taking the message to the amygdala, the emotional part of the brain.
Kerstin Uvnas-Moberg, one of the earliest scientists to focus on oxytocin, did experiments with male rats to test whether the release of oxytocin could be stimulated by senses other than touch. Oxytocin reduces sensitivity to pain; when Moberg injected some male rats with oxytocin, their cage mates also became calmer and less stressed.
Giving the male rats that did not receive oxytocin an antagonist -- a chemical to block oxytocin's effects -- eliminated this effect in the cage mates, as did blocking their ability to smell.
These experiments showed two things: that the oxytocin systems of the cage mates had been activated, and they'd been activated through the sense of smell.
Moberg believes that this same smell effect happens in humans with oxytocin, although human experiments haven't been done.
We know that being around someone calm can help us chill. It may be that getting a whiff of the oxytocin she's putting out tells our own bodies to give up a little of the good stuff.
Moberg is author of "The Oxytocin Factor;" she's applied for a patent for the use of oxytocin to treat the symptoms of menopause.