In anatomical terms, our sense of smell is linked with the limbic system, commonly called the forebrain. Generations of early researchers, including Paul Broca and James Papez, entertained the notion that the limbic system represented the oldest and simplest – in other words, stupidest – parts of the brain, which are also associated with pleasure, reward, impulse-control and addiction. Loss of the ability to smell (anosmia) was linked with mood-disorders and depression. And naturally, this discussion led to linking the sense of smell with libido, our all-you-can-eat cravings for wanton sex and limitless potato-chips (whichever comes first).
A half-century ago, American researcher Paul D. MacLean further suggested that the human brain included what he called a reptilian complex; we still use the term "reptile brain" today as pseudo-scientific shorthand to refer to our primal impulses at their most lizard-like, irrational and amoral.
If this sounds a bit quaint, by the way, consider how the manufacturers of products manipulate consumer behavior, also known as sales, with the addition of fragrance. The household detergent, Tide®, even has its own Facebook page because some people love the product's smell that much.
Peter Friis, founder of the new aromatherapy brand Essio, is a young Los Angeles-based entrepreneur who is obsessed with the effects of fragrance. In the case of his new brand, one of six proprietary fragrance-blends in the form of 100 percent organic essential oils is diffused into the warm flow of the shower. The blends are created to affect moods, even to relieve insomnia. "We know from current research that the human nose can detect about 10,000 distinct aromas," says Friis. "Every fragrance is actually a combination or mosaic of fragrance molecules, including our aromatherapy oil blends for the shower. It's the complexity of each olfactory experience, which makes it so alluring and mysterious, and makes a memory associated with a specific smell so long-lasting. Science shows that memories and emotions anchored with odors become hard-wired into the brain."
Friis' reference to the 10,000 detectable – sometimes delectable – aromas available to the human nose is based upon the 2004 Nobel-prize winning research of Richard Axel and Linda B. Buck.
In their series of pioneering studies which clarified how our olfactory system works, joint-recipients Axel and Buck discovered a large gene family, comprised of some 1,000 different genes (three percent of our genes) that give rise to an equivalent number of olfactory receptor types. These receptors are located on the olfactory receptor cells, which occupy a small area in the upper part of the nasal epithelium and detect the inhaled odorant molecules.
The healing powers of aromatherapy, like many aspects of olfactory study, are speculative and controversial. For instance, lavender (the familiar, soapy-smelling flowering plant from which we derive our word "lavatory") has been used across Europe for centuries not only as a mild antiseptic, but also as a calming agent which enhances well-being.
While it is tough to argue with the anecdotal folk-tradition of lavender and dozens of other essential oils, lab results are less than conclusive, in part because the wild botanical samples themselves are highly variable.
This time of year, with the celebration of Valentine's Day, the most disputed element of olfactory communication is brought to mind: pheromones. Pheromones are chemical signals sent by many organisms, including amorous housecats, butterflies, honeybees, and even green algae and slime molds! Observing pheromone-driven behavior among our fellow-creatures may make us want to hum the Cole Porter classic "Let's Do It." But although we may feel the call of the wild, the role of pheromones in human physiology and behavior invites skepticism from science.
While some butterflies and moths use pheromones to attract a potential mate from up to six miles away, and certain plants release "alarm pheromones" when they are being munched, prompting surrounding plants to produce tannins which make them unappetizing to grazing animals, there is disagreement even about the mere presence of the human vomeronasal organ (VMO), ostensibly located at the base of the nasal septum. Some scientists maintain that the VMO is present in the human fetus, but that this chemosensory organ recedes into non-existence by the time an infant is born. The absence of this organ would mean that as a species we are unable to produce or process pheromones.
Still, the role of fragrance in human interaction, especially in pursuit of the erotic and romantic, is undeniable. Peter Friis comments, "We can't guarantee that the blend of Moroccan Rose, Patchouli and Cinnamon essential oils will bring you true love. But in my experience, being freshly-showered
never hurts."

Passion: It is as Easy as Breathing

Our primary sense of smell, seated in the limbic system of the brain, triggers emotions and our most primal cravings for pleasure. Some fragrance-experts theorize that aromas, as well as undetectable chemosignals called pheromones, even make us fall in love. Here are a few botanical sources for essential oils used in aromatherapy long-believed to trigger romance, passion and
sexual attraction:

• ROSE OIL – One of the most costly essential oils, and perhaps the most romantic. Rose Maroc in particular has a deep, relaxing floral sweetness with an after-note of spice.
• PATCHOULI OIL – Smoky, sexy and undeniably sultry, this ancient aromatic is the "bad girl" cousin of common Mint varieties. Along the fabled Spice Route, merchants used fragrant Patchouli leaves to keep their silk and textiles fresh-smelling and moth-free.
• CINNAMON OIL – Peppery and energizing with a slight, bark-like sharpness. The dark, warm spiciness of this ancient, edible aromatic triggers olfactory memories of everything from hippie incense to batches of fresh-baked cookies.
• LAVENDER OIL – The basis of many aromatherapy products and treatments, this beloved botanical has a sweet yet deeply clean and purifying fragrance.
• CITRUS OIL – Bright, tangy-acidic and slightly astringent. The upbeat, zesty fragrances of bergamot, citron, lemon, lime and orange are natural depression-zappers.