In a recent study published in Nature [1], neurobiologists show how pheromones emitted by the female moth induce the male moth to alter his flight pattern, zigzagging closer and closer until he finally homes in on the source of the airborne attractant. Although the authors of the study are optimistic that their findings will shed light upon the relationship between odor and behavior in humans, until human pheromones are purified and bottled, perfume-wearers among us can but hope to alter the behavior of potential mates as does the female moth.

In the meantime, perfumers have to make do with the approximately 3,000 natural and synthetic compounds already present in their arsenal. Additionally, they have to contend with the diminished sense of smell in humans. The human genome encodes between 500 and 750 olfactory receptors, which are expressed in the sensory neurons of the olfactory epithelium, but over half of these appear to be nonfunctional pseudogenes. It is thought that as human survival became less dependent upon olfactory acuity, the selective pressure to maintain functional receptors eased up. Our remaining functional receptor genes allow us to distinguish between 3,000 and 10,000 different odors. The neurons of the olfactory epithelium connect into the amygdala, the "emotions" center of the brain, and the hippocampus, where memories are stored. This may explain why scents can affect moods and are such powerful reminders of things past.

A perfume comes into being when a distributor, such as Estée Lauder or Calvin Klein, puts together a "brief," which describes the image of the hypothetical client. For example, a brief may invoke a sophisticated, self-sufficient woman accustomed to brokering multilateral transactions and for whom international travel is routine. She needs a versatile scent that works both during the day while she works, as well as for dinner out later in the evening. "Suppliers" or "oil houses," the companies that produce the perfume, will immediately set to work. In the past, perfumes were often formulated over the course of a year or two, but in today's competitive climate, perfumes are formulated in a matter of weeks. The perfumer, who actually composes the scent, works hand in hand with a team of advisers, including organic chemists, sensory psychologists, and consumer researchers.

Factors they consider are the volatilities of the various components. Perfumes are constructed in layers, with the top "note," as it is called in the industry, consisting of highly volatile compounds that will evaporate in a matter of minutes. The "middle" and "base" notes will diffuse in a matter of hours and days, respectively. Thus, the scent will evolve over time, making it possible for the worldly executive to smell fresh and citrusy while she works and, perhaps, exude a richer, more sensual fragrance in the evening.

Organic chemists will ensure that the components of the scent can withstand the changes in pressure and climate integral to her world-traveling lifestyle. The sensory psychologists, in turn, will make sure that the scent taps into positive emotions and memories. For example, the smell of baby powder is one of the best-loved scents in the United States, almost certainly due to its association with freshly bathed babies. Consumer researchers do their jobs by assessing the kinds of scents that are currently in vogue and, once the scent has been composed, by gathering feedback to be used by the perfumer in formulating the final submission. In addition, "evaluators," who have an extremely keen sense of smell, will provide the perfumer with feedback and, thus, help shape the perfume as it is developed.

In addition, perfumers are increasingly considering the principles of "aroma-chology" in designing their perfumes. Although there are differing viewpoints as to its worth, aroma-chology purports to alter moods through the use of scents. Anne Richardson, sensory sciences development manager at Quest International in London, explains that there are measurable changes in patterns of brain activity when people smell a fragrance. "The question then arises," she says, "of what you can actually deduce from that. Is there a real mood change?" While the jury is still out on its scientific merits, there is no doubt that consumer interest in aroma-chology products will ensure that its tenets are considered in the design of many fragrances today.

Organic chemists are critical to the perfume industry. Perfumers work closely with them and also have training in the chemistry discipline themselves. Organic chemists can synthesize new scents using "headspace technology," in which a scent from a fragrant flower found in the wild can be analyzed and recreated in the laboratory. Headspace technology makes use of a device that can capture a scent onto absorbent beads, to be coaxed out later and analyzed into its components by gas chromatography and mass spectrometry. A company called Aveda has recently used headspace technology to capture the scent of Mojave Desert flowers that have bloomed for the first time in 100 years thanks to the rains brought on by the 1998 El Nino. In a still more creative use of the technology, a team from Quest International has isolated scents from underwater coral reefs off the coast of Madagascar. In addition to recreating natural scents, chemists also seek to synthesize novel fragrant compounds in the laboratory.

Organic chemists also generate the multitude of synthetic compounds that make up most perfumes today. Although a few companies exclusively use natural products and scorn the use of synthetics, the advent of synthetic compounds is generally viewed as an improvement in the industry. Some botanical oils extract poorly, and some flowers, however intoxicating their scent, are too rare to be commercially useful. Aromatic compounds previously isolated from animals are now almost entirely synthetic, much to the relief of animal rights activists and animal lovers alike. Synthetics are said to give sparkle and freshness to a fragrance, balancing and bringing out the best in the heavier natural oils.

Microbiologists also have their place in the perfume industry. Robertet, a supplier based in Grasse, in southern France, has developed an aromatic compound called Diomix, which has bacteriostatic properties. When Diomix is metabolized by body-odor-causing bacteria such as Staphylococcus epidermis, compounds that inhibit their growth are released, thus providing an environmentally friendly alternative to the antimicrobials currently used in deodorants. In addition, neurobiologists are using their knowledge of the signal transduction pathways that lead to the perception of odors to assist in the design of malodor counteractants. Malodor counteractants will typically act on the malodorous compound itself or on the olfactory receptor to which it binds, acting as a competitive inhibitor.

Although the design of fine fragrances is certainly the most glamorous sector of the industry, a much larger number of individuals work to design the fragrances added to a wide variety of consumer products such as soaps, detergents, cosmetics, air fresheners, and diapers. The jobs of these lesser-known perfumers may, in fact, be more challenging. A fragrance added to a detergent must mask the odor of the detergent itself and, in addition, smell good in the box, the washing machine, the dryer, and after having been subjected to a steam iron. Unglamorous they may be, but fragrances designed for household products typically bring in much more revenue for a supplier than fine fragrances.

So how does one become a perfumer, or a "nose," as they are called in the industry? In the past, the craft was passed down from father to son, and perfumery was dominated by a few families in the vicinity of Grasse, France. Nowadays access to the profession is more democratic, and one can attend a perfumery school. One of the better known schools is L'Institut Supérieur du Parfum, de la Cosmétique et de L'Aromatique Alimentaire (ISIPCA), located in Versailles, on the outskirts of Paris. A second one, in Paris, is run by the supplier Givaudan. Admission to either is extremely competitive, and one must demonstrate an exquisitely discriminating sense of smell to gain entry.

Once in the work force, aspiring perfumers can work in a variety of settings. Evelyne Robert of ISIPCA says that graduates of her institute will typically work for one of the multinational suppliers, such as International Flavors and Fragrances, Firmenich, Quest International, or Robertet. In addition, perfumers are employed by smaller, regional houses that generate a more limited range of products and have more limited research capabilities. Also on the rise are perfumers who work independently and create customized perfumes. The perfumer will meet with an individual client and, after assessing his or her personality and particular likes and dislikes, will create a customized fragrance. Finally, Jean Patou and Chanel, rather than working with outside suppliers, employ their own noses.

Besides those who actually work to formulate a perfume, the industry also relies heavily upon those who design the bottle and packaging and on those who market it. Annette Green, president of the Fragrance Foundation explains that a perfume must appeal to the senses of sight and touch in addition to the sense of smell. The packaging and bottle must be attractive and reflect the scent within. In terms of marketing, eye-catching advertisements, scented strips in magazines, promotional events in department stores, and celebrity endorsements all contribute to the buzz surrounding the launch of a new perfume.

In addition, technology may yet come to the assistance of perfume companies' marketing departments. DigiScents, a company based in Oakland, California, has developed ismell, a speaker-sized device that can be connected to a personal computer's USB port and used to transmit fragrances into homes or offices. By mixing and matching an array of fragrant compounds, ismell can transmit thousands of different smells and can be used, among other things, to market scented products online. At a cost of approximately $200, ismell is affordable, and, according to David Libby of DigiScents, although the device has not yet been launched, it has already generated significant interest. "To date, we have more than 5,000 Web, software, and video game developers signed up on our Web site who have requested the tools needed to learn how to add scent to their media," he says.

In reading a Webzine, you thought you had escaped the headache-inducing "scented strip" phenomenon so common in hardcopy magazines? Just in the nick of time. Soon an article such as this will likely be peppered with illustrative examples of scents used in perfumes today - just a click of a mouse away! Sometimes one has to wonder if technology truly does bring improvements.