Ever find yourself becoming nauseous in the close company of gushing, overeager lovebirds? Besides the fact that the couple may be overtly exchanging saliva and groping each other with the modesty of zoo apes, your disgust could have something to do with fragrance sensitivity.

Hypersensitivity to airborne chemicals and other social contaminants (perfumes, cosmetics, lotions, soaps, and oils) has been a long-standing source of irritation to many individuals. Even major magazine publishers offer subscribers alternative editions of their mags without the stinky perfume ads, if you ask 'em nicely.

The chemistry of sexual attraction creates a similar release of fragrant contaminants. When people fall in love, a chemical peptide called phenylethylamine is created by the brain and released throughout the body, causing feelings of euphoria and ecstasy, and commands the driving force of sexual desire. Love also causes the creation and release of norepinephrine and dopamine. These chemicals' effects are molecularly similar to amphetamines, and can be highly addictive.

According to experts at Australia's Monash University, output of phenylethylamine can be initiated by something as basic "as the meeting of eyes or the touching of hands. The heady emotions linked to racing pulses, sweaty palms and heavy breathing can be clinically explained as the result of an overdose."

In The Chemistry of Love, Michael Liebowitz says phenylethylamine is crucial to courtship, causing a high arousal state, increase in heart rate and white blood-cell production, reduction of lactic acid levels in the blood, and initiates "boundless energy" similar to "symptoms of temporary insanity."

Should one lover move on prematurely (drop the other like a hot potato), it's not uncommon for the loser left behind to suffer intense pains of withdrawal, duplicitous with a narcotic love-jones. It's a nice high, but some consider phenylethylamine a gateway drug to more deleterious dope.

When people first fall in love, phenylethylamine is at peak production, but rarely lasts more than a couple years.

As relationships mature, phenylethylamine is replaced with endorphins (edogeneous morphine), which induce milder sensations of well-being, peace, and security. Also, during sex, oxytocin is released, producing feelings of satisfaction and attachment.