What the Nose Knows: The Science of Scent in Everyday Life (14 page)

Beer brewing used to be a strictly local operation, but today’s American beer market is dominated by national brands like Miller and Budweiser. It is no coincidence that in the last fifty years the amount of malt in the average American brew has declined more than 25 percent and the amount of hops more than 50 percent. In other words, beer is less bitter and less aromatic than ever. Big brands expanded through a strategy of making inoffensive beer. They traded character for market share. The good news is that the microbrewery movement is thriving. Small producers have created distinctive beers with greater flavor and more interesting aromas. These so-called “craft” beers are on the rise, while overall domestic beer sales are flat or declining.

It is tempting to think of odor blanding as a typical expression of American mass-market consumerism. Yet it’s a truly global phenomenon. France, a country not known for its welcoming attitude toward American culture, is home to some of the world’s stinkiest cheeses: St.-Nectaire, Ami du Chambertin, and Epoisses. (The last is said to smell simultaneously of “socks, wet dog, and manure.”) France has more varieties of cheese on sale today than ever before; roughly a hundred new varieties hit the market annually. Paradoxically, these products are tasting more and more alike. Traditional mold-ripened cheeses, made from unpasteurized milk, change in texture, smell, and taste as they age. The new versions are made from pasteurized and ultrafiltered milk; they are built for a long and consistent shelf life. Industrial brie—rubbery, flavorless, and never-aging—is taking over the market.

French manufacturers go to great lengths to create an aura of authenticity for the new fromage-blah; they package it in a wooden box, wrap it in plastic straw, and give it an impressively historical name. In trade jargon, these impostors are known as
vrai-faux produit traditionnel
; think of it as cheese that is “fake but accurate.”

Coffee Beans and Other Bad Memes

Joel Lloyd Bellenson places a little ceramic bowl in front of me and lifts its lid. “Before we begin,” he says, “you need to clear your nasal palate.” I peer into the bowl. “Coffee beans,” explains Bellenson’s partner, Dexster Smith. “This is what they use in perfume stores. It’s like the reset button.” Dutifully, I reinitialize my nose by sniffing the beans.

—C
HARLES
P
LATT,
Wired
magazine, 1999

Charles Platt began his
Wired
cover story with this vignette about the two founders of DigiScents, Inc. Joel and Dexster had come up with a small unit that could release innumerable combinations of scent when activated by a digital signal from a personal computer. Stanford graduates, with degrees in bioscience and engineering, respectively, they had previously started a successful genomics company. Neither of them knew beans about smell. That’s why I had been hired a few months earlier—to bring a working knowledge of sensory science and the fragrance industry to the new venture. I thought their coffee stunt was silly. I’d seen beans at a trade show, but had never heard of a perfumer using them. Still, Joel and Dexster had an unerring sense of publicity—a useful talent for founders of a Silicon Valley startup. So I sat back and watched with inward eye-rolling as the meme of a “reset button for your nose” was launched into digital culture.

The bean meme is now a fixture in perfume retailing. I toured the Mall at Short Hills, New Jersey, recently and marveled at how thoroughly it has taken root. At the
Angel
counter in Nordstrom a glass cone full of coffee beans was held aloft on a brushed metal stand. In Bloomingdale’s the beans were in a cocktail glass. The Jo Malone display in Saks had them in an apothecary jar with a metal lid. It’s all good fun and marketing, but there is not a jot of science behind it. (There are twenty-seven aroma impact molecules in roasted arabica coffee—how could smelling all these help clear the nose?) I don’t make an issue of it when I’m shopping, but a perfumer of my acquaintance was once ejected from a Nordstrom in Seattle for disputing the bean meme a little too persistently with the lady behind the counter.

The idea of a reset button for the nose goes back a long way. At nineteenth-century Japanese incense parties (which were part guessing game and part poetry contest), it was customary for participants to rinse occasionally with a mouthful of vinegar to keep the sense of smell sharp. American perfumers in the 1920s sniffed camphor to restore sensitivity after a hard day at the office. The pioneering odor classifiers E. C. Crocker and L. F. Henderson routinely sniffed camphor or ammonia to “refresh the nose” during long smelling sessions. It’s not clear if these practices worked as intended, or if they are just testimony to the olfactory placebo effect. Similarly, contemporary food companies require taste-test panelists to rinse between samples. The rationale—that it minimizes flavor carryover—seems so commonsensical that no one bothered to test it until 2002. When a sensory lab finally got around to it, the results were surprising. In the study, trained tasters rated the bitterness of cream cheese samples mixed with different amounts of caffeine. (Caffeine is notorious for the delayed onset and lingering aftertaste of its bitterness.) Between samples the tasters tried all sorts of lab-standard palate-cleansing techniques: they rinsed with water or with sparkling water (up to six times); they ate carrots or crackers or plain cream cheese. The results were all the same—cleansing the palate made no difference to subsequent judgments of bitterness. Caffeine leaves a bitter taste, but panelists can compensate for it as they move from sample to sample. So go ahead—serve bread and crackers at your wine tasting, and enjoy the between-course sorbet at your fancy French restaurant. Just don’t expect either habit to make your palate sharper.

According to discriminating foodies, red wine should be paired with only certain kinds of cheese. Aged Gouda, Dry Jack, and Manchego enhance the flavor of red wine, while blue cheese and triple cream varieties interfere with it. At least that’s the dogma. Like many rules of cuisine, the logic behind wine and cheese pairings has seldom been put to a scientific test. The sensory specialist Hildegaarde Heymann and a graduate student addressed the question head-on. They trained panelists to rate red wines along a number of sensory dimensions. When wines were paired with eight different cheeses, the tasters’ perception did indeed change, but not for the better. The flavor of the cheese accentuated the butteriness of the wines, but it blunted every other sensory characteristic—probably not what one wants when uncorking a valuable vintage.

Wine-tasting tradition holds that a wine must be drunk from the correct glass: reds from a large, bulb-shaped one that tapers at the mouth, whites from a smaller version of this, or perhaps from one that isn’t tapered. The idea is that the size and shape of the glass determine how the aroma is collected and delivered to the nose, and that there is an optimal glass for each type of wine. Do these rules have a basis in fact, or are they simply the pretension of wine snobs? Only three studies have addressed the question, and the results are mixed. In one, a Mondavi cabernet smelled less intense in the traditional big-bulb Bordeaux glass than in other shapes; other sensory measures (fruitiness, oakiness, etc.) were unaffected by glass shape. Another study served red and white wines in five different glasses and found that shape altered the perception of the wines on nearly every rating scale. Why such different results? For one thing, the first study was done with blindfolded subjects and the second one was not. A judge’s expectations about the wine change when the glass can be seen. A third study found that tapered, bulb-shaped glasses produced a stronger impression of wine aroma than a tulipshaped or a nontapered bulb. This effect disappeared, however, when the odor sensitivity of individual judges was taken into account. Only people with superior noses could appreciate the subtle effects of glass shape. While this will no doubt reinforce the self-regard of wine snobs, the final joke is on them. The study presented a single wine in glasses of various shapes; afterward most judges thought they had been served two or three different wines. Another triumph of the visual over the aromatic. In the final analysis, glass preferences may be nothing more than a tradition. In a similar way, I have heard French perfumers insist that their style of smelling blotter (folded lengthwise into a V-shape, and cut to a point on the end) is superior to the thin, rectangular version used by Americans. Why? Because it allows the perfume to evaporate more precisely. The world of olfaction is filled with irrational beliefs, and sometimes that’s just part of the fun.

CHAPTER 6

The Malevolence of Malodor

And when euyl substance shall putrifie,

Horrible odour is gendred therbye;

As of dragons & men that long dede be,

Theire stynche may cause grete mortalite.

—T
HOMAS
N
ORTON
,
Ordinall of Alchimy
(late fourteenth century)

O
N A LATE
-S
EPTEMBER
S
UNDAY IN 1971,
I
WALKED
along a dusty footpath toward some oak woods near San Rafael, California. I was with a few oddly dressed friends: the men wore tights and jerkins, the women long-sleeved, flowing dresses and conical hats. I wore a Puritan robe with white collar and carried a wooden recorder. We were in a long line of costumed people stretching from a field of parked cars to the crest of a hill, where flew the pennants of the Renaissance Pleasure Faire. The wooded hills of Marin County were a congenial spot for this deliberate flight of fancy into the past.

Amid the bawdy puppet shows and the racket of tambours and sackbuts, one could almost slip into the mental habits of an earlier time. In Elizabethan England, bad-smelling air was thought to be the cause of disease. In
Hamlet
, Shakespeare wrote: “’Tis now the very witching time of night / When churchyards yawn, and hell itself breathes out / Contagion to this world.” According to Simon Kellwaye in
A Defensative Against the Plague
, written in 1593, illness results from “some stinking doonghills, filthie and standing pooles of water and unsavery smelles.” In a time before indoor plumbing, when open sewers were the norm, there were enough “stinking doonghills” to make everyone feel threatened by disease. For Elizabethans, however, odor was both a cause and a cure. They believed that good odors could ward off disease. This led them to hang spicefilled pomanders from necklaces and to fumigate their houses by burning incense, sulfur, and gunpowder. Beneficial aromas were so sought-after in times of plague that price-gouging was common. A writer in 1603 complained that rosemary, “which had wont to be sold for 12 pence an armefull, went now for six shillings a handfull.”

Twenty years after the Pleasure Faire, people in Marin County were once more channeling a Medieval mind-set, and this time it wasn’t fun and games. Like a pitchfork-wielding rabble demanding protection from plague-inducing vapors, antifragrance activists were out to ban perfume because they believed it was making them sick. They objected not just to perfume, but to the lingering scent of shampoo, body lotion, hair spray, deodorant, laundry detergent, and fabric softener. Protesting at a perfume industry meeting in San Francisco, activists wore respirators and carried a prop barrel labeled
CALVIN KLEIN
and
TOXIC CHEMICALS
. The “disability coordinator” for the San Francisco mayor’s office joined the fray. “Ten years from now it will be politically incorrect to wear perfumes in public,” he proclaimed. Even by the flamboyant standards of the Bay Area, this was great political theatre. But it raised an important question: Can a smell actually make us sick?

T
HE PROTESTERS
were people who suffered from what they called Multiple Chemical Sensitivity, or MCS. They claimed to be so sensitive to chemicals in perfume that the slightest whiff would trigger symptoms. I spoke with several MCS patients at the time, and was struck by how unhappy and miserable they were. Their extreme efforts to avoid scented people and smelly places made them virtual shut-ins. One woman had moved her family to the Arizona desert in the hope that living in an isolated trailer custom-built with “nontoxic” metal and tile surfaces would solve her problem. It didn’t. It was clear to me that these folks were genuinely distressed and deserving of sympathy. What wasn’t clear to me was the nature of their illness.

Despite numerous investigations by medical experts and public health authorities, including the World Health Organization, there is no precise definition of MCS. According to a paper in
Occupational and Environmental Medicine
, it is “a poorly understood and controversial syndrome. Common symptoms include fatigue, difficulty concentrating, pounding heart, shortness of breath, anxiety, headache, and muscle tension. They occur ‘in response to demonstrable exposure to many chemically unrelated compounds at doses far below those established in the general population to cause harmful effects. No single widely accepted test of physiological function can be shown to correlate with symptoms.’” The American Medical Association looked into MCS and decided in 1991 not to recognize it as an official diagnosis. In the meantime, MCS has been renamed Idiopathic Environmental Intolerance (or IEI) to reflect the fact that it has no known cause (i.e., it is idiopathic).

Amid all this confusion, IEI patients are consistent about one thing: they claim to be far more sensitive to odors than are other people. This is an easily testable proposition, and numerous studies have compared the olfactory sensitivity of IEI patients and healthy controls (matched for age and sex). The results consistently show no difference between the groups in odor-detection thresholds. In this strict sense, IEI sufferers are no more sensitive to odor than anyone else.

There are some differences in how IEI patients and healthy people respond to odor, however. For example, patients find the rosy scent of phenylethyl alcohol less pleasant than nonpatients, and they are more likely to report eye/nose/throat irritation in response to it. In another test, IEI patients and controls were confirmed to have similar levels of odor sensitivity. They were then exposed for ten minutes to unscented air or to air with a barely detectable level of 2-propanol (rubbing alcohol). Only 10 percent of normal volunteers reported physical symptoms in either condition. In contrast, 30 percent of the patients reported symptoms to both scented and unscented air. This exaggerated subjective response implies a difference in cognitive processing rather than a change in sensory perception. In other words, a patient’s brain intuits harm from a sensory message that causes no alarm in a healthy person.

T
HE NATURAL HISTORY
of odor aversions helps put IEI in perspective. Even the most innocuous scent becomes objectionable if it reminds us of an unpleasant experience. Take the case of Izabella St. James, a former girlfriend of Hugh Hefner who did not enjoy her time at the Playboy Mansion. It was apparently Hef’s habit to prepare for festivities in the bedroom by coating himself in baby oil. To this day, says Ms. St. James, the smell of baby oil makes her gag.

Then there is Rolf Bell, a tall, athletic guy in his mid-fifties. When he was six or seven years old, his family visited Mount Lassen in Northern California. They stopped for a picnic at Bumpass Hell, a geothermal area full of boiling mud pots and steaming fumaroles. His mother had prepared egg-salad sandwiches for lunch. After eating his amid clouds of sulfurous steam reminiscent of rotting eggs, little Rolf was left with a permanent olfactory aversion: he hasn’t eaten egg salad since.

We sometimes create odor aversions in a misguided attempt to avoid truly bad smells. It’s a common impulse to mask the smell of decay with a strong and less objectionable odor. The men who collected the bodies of those killed in the 1900 Galveston hurricane were encouraged to wear bourbon-soaked handkerchiefs over their faces, or to smoke strong cigars. Similar advice was given to personnel in the American Graves Registration Unit who searched the European battlefields of World War II for the remains of U.S. servicemen. Sadly, experience shows that a masking scent may become linked to the emotional trauma of body retrieval duty. Today’s military personnel are told not to use cologne to cover the stench.

In January 1987, in the outskirts of Hesperia, a town in San Bernardino County, northeast of Los Angeles, sat a nondescript aluminum building on an asphalt-and-dirt lot surrounded by a chainlink fence topped with barbed wire. The owner of a nearby business noticed flames shooting out of the building’s smokestack. What really grabbed his attention was the smell of the smoke: something he hadn’t smelled since his U.S. Army unit walked past the ovens at a liberated concentration camp in Germany more than forty years earlier. It was the sickening, strangely sweet odor of burning human flesh. His phone calls to local officials began an investigation that uncovered the largest funeral home scandal ever in Southern California, a grim story of stolen body parts and gold fillings and illegally commingled remains.

These are the smells people can’t forget, even if they want to. I’m not talking about clove oil reminding one of a visit to the dentist’s office; I’m talking about the extreme edge of human experience. Smells associated with intense trauma leave an indelible impression. Take the case of a fire department paramedic who was called to treat a garage mechanic injured when an automobile tire exploded. The paramedic tried mouth-to-mouth resuscitation, but the victim’s face was so badly damaged he had trouble locating the mouth. The victim vomited on him and died. The paramedic was found hours later, sitting in a daze in his car in the middle of an intersection. The smell-linked trauma haunted him for years—whenever he encountered a foul odor, it would bring on a sudden attack of nausea.

The Boston psychiatrist Devon Hinton and his colleagues regularly treat Cambodian refugees, many of whom witnessed atrocities during the Khmer Rouge reign of terror between 1975 and 1979. Olfactory-triggered panic attacks are frequent among these survivors. Innocuous smells such as car exhaust, tobacco smoke, and roasting or frying meat can set off anxiety, dizziness, nausea, and a racing heartbeat. These symptoms are sometimes accompanied by flashbacks to horrific scenes that took place amid the smell of exploding ordnance, and the stench of burned bodies and corpses in open mass graves. Hinton’s case summaries vividly record the inhuman savagery that Pol Pot inflicted on his own people, and demonstrate the power of smell to forge a perpetual link to strong emotions.

How to Create an Odor Phobia

Omer Van den Bergh makes people sick. He is a researcher at the University of Leuven in Belgium who has developed a surefire way to induce temporary (yet harmless) physiological distress. He does it by increasing the carbon dioxide level in the air, a simple move with unpleasant consequences. Within twenty seconds of breathing CO
₂
-enriched air, a person experiences tightness in the chest, a feeling of choking or smothering, a pounding heart, sweating, hot flushes, and anxiety. The symptoms disappear quickly when the CO
₂
is reduced to normal levels.

Van den Bergh uses CO
₂
to explore the psychological mechanisms of odor aversion. In the basic setup, a volunteer breathes scented CO
₂
-enchanced air and experiences the usual unpleasant symptoms. When the volunteer returns to the lab the next day and breathes normal air with the same scent, he feels ill again—though there is no physical basis for the reaction. Van den Bergh has conditioned his subjects to feel sick in the presence of an odor, just as Pavlov conditioned his dogs to salivate at the sound of a bell. Remarkably, all it takes is a single episode of physical distress to turn an odor into a trigger for illness. Van den Bergh calls this process “symptom learning,” to reflect the fact that it’s a form of associative learning, a basic process by which organisms respond to their environments. Symptom learning works better with malodors, such as ammonia and butyric acid, than with a pleasant, fresh scent like eucalyptus.

Another hallmark of learned aversion is that it spreads from one odor to another in a process known as stimulus generalization. For example, when Van den Bergh conditioned people to become ill at the smell of ammonia, he found they would experience symptoms in a later test when the air was scented with another unpleasant odor, such as butyric acid (smelly feet) or acetic acid (vinegar). The subjects would not become ill to an entirely different smell such as citrus, however. Generalization to related odors can happen as long as a week after the initial event. One consequence of this is that a brief exposure to a sickness-inducing smell leaves a person psychologically vulnerable for days to acquiring additional odor triggers.

If an odor aversion can form after one exposure, and if the aversion can generalize to similar smells, what stops it from becoming a psychological chain reaction? Why isn’t everyone gagging all the time? The answer is a phenomenon called extinction. When an illness-associated odor is repeatedly presented without elevated CO
₂
, the Pavlovian response eventually fades away as the brain unlearns its conditioned response. When the odor no longer triggers symptoms, the response is said to have been extinguished. Therapists use the extinction phenomenon to help people overcome phobias to spiders, closed spaces, and so on; they call it systematic desensitization therapy.

Bad smells are natural candidates for Pavlovian conditioning, but even pleasant ones can trigger symptoms, as we saw in the example of cologne-wearing soldiers on body retrieval duty. Pleasant scents can become triggers under less dramatic circumstances, if they are given the proper psychological “spin.” In another of his experiments, Van den Bergh had test subjects read a leaflet beforehand, which discussed chemical pollution and described a patient with MCS. (The text was lifted from an environmentalist website.) In the experiment, the pamphlet’s negative spin increased CO
₂
-induced illness to pleasant as well as unpleasant odors. Thus, even a nice fragrance becomes a trigger for acquired illness if one believes, for example, that its chemical composition is harmful. Van den Bergh sees an irony in this: “warnings and campaigns against environmental pollution, while having important beneficial effects for the environment, may inadvertently facilitate acquiring symptoms to chemicals in the environment and promote the spreading of MCS, mass sociogenic illness, and the like.” In other words, we might scare ourselves sick.