Biologically speaking, love is seen as a means of cementing a relationship so that the couple is able to mate and produce healthy, well-cared for offspring. Love as a means of keeping a couple together might work via two possible mechanisms. The first is simply an increased connection that person. Thus, we would expect, that those in love might release hormones or have other biological changes which promote dependency, trust and happiness. The fact that feelings of love correlate to releases of dopamine, serotonin and norepinephrine (which stimulate pleasure and reward centers in the brain) supports this mechanism. However, love could act to maintain a relationship by another pathway. It could function to make other partners less desirable, thus decreasing the urge to mate with someone else. It's this mechanism that the study examined.
Humans are remarkably capable of identifying the sweat of people who they interact with on a regular basis. That same sweat also functions to make a man seem hotter and turns women on. Women are even able to identify men with different immune genes simply based on the smell of their sweat, something that makes men more attractive. So researchers from the University of Pennsylvania sought to determine if smelling is affected by levels of passion and love in a relationship. If scent is key in both attraction and recognition, being less able to recognize sweat smells might decrease the chance of a woman wanting other guys.
The nose knows.
So they had women take a survey to determine their level of passion for their partners. They then had the partners, a close male friend, and a close female friend all sleep for one week in t-shirts with special absorbent patches sewn to the armpits. They then tested the women's ability to identify their partner's smell. On average, the women could - 5.2 out of 7 tries they picked out their man. They also had no difficulty identifying the smell of their female friend. But when the women tried to identify their male friend, their level of passion in their relationship had an inhibitory effect - those that were really in love couldn't do it while those that were feeling less amorous had less trouble. Thus the love they have for their partner is somehow biologically inhibiting the women's ability to recognize the smell of other men.
The researchers are now looking directly at the women's brains while they sniff the different smells. Preliminary results show that while sniffing the sweat of friends, the areas of the brain responsible for recalling information light up, whereas smelling strangers activates centers associated with fear. Most interestingly, smelling lovers activates pleasure centers. So scent might function in both drawing a person closer to their partner and reducing the attractiveness of others.
In other words, it might do you some good to lay off the cologne and get a little sweaty around your girl, though I wouldn't go too overboard. Her smelling your B.O. a little bit more might just keep her interested and help deter her nose from following other scents, which in turn might deter her eyes from wandering to other guys. If you shower constantly or completely distort your smell with the cologne and aftershave usage of a preteen boy at a coed dance, you might just find her nose isn't the only part of her that ends up where it doesn't belong.
J LUNDSTROM, M JONESGOTMAN (2008). Romantic love modulates women's identification of men's body odors Hormones and Behavior DOI: 10.1016/j.yhbeh.2008.11.009