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A Sense of Smell Friendly

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PUG OR POINTED, PATRICIAN OR PEDESTRIAN, the nose knows. And when it doesn’t, it’s good to know about the Nasal Dysfunction Clinic at the University of California, San Diego, one of a few of its kind in the country and the only one on the West Coast.

About 2,500 patients a year visit the clinic, says its director, Dr. Terence M. Davidson, who’s also a professor of surgery at UCSD and the associate dean for continuing medical education at the school. These are folks whose family doctor, or perhaps even an ear-nose-andthroat specialist, hasn’t been able to help. Most seek relief from chronic sinusitis—inflamed sinuses that cause facial pain, pressure, congestion and a host of other unpleasant and fatigue-inducing symptoms. Another specialty of the clinic is sleep apnea, a temporary stoppage of breathing during sleep often caused by obstruction of the airway.

While fewer in number than sufferers of these two disorders, another batch of patients seen at the Nasal Dysfunction Clinic have lost their sense of smell, a condition known as anosmia. It’s estimated that about 1-2 percent of the population has a significant degree of anosmia, Davidson says, which translates to 5-10 million people. Smell loss also is common in dementia and Alzheimer’s disease, affecting another 10-15 million, and 30-40 million have their smell impaired by sinus and allergy problems.

The most common complaint of people who have lost their sense of smell is the accompanying loss of taste, because about 95 percent of the sensory input from food is derived from its aroma. Not being able to enjoy food is nothing to sneeze at, but the primary function of smell is to serve as a warning signal.

“Our sense of smell allows us to test our environment,” Davidson says. “It tells us about a skunk, sure, but also smoke from a fire and poisoning from spoiled food.”

Smells also help us bond with our environment. Women have always known this, Davidson says, sensitive as the distaff side is to body aromas and fragrance, but men use smells for bonding, too.

“When a man puts his son in a headlock, with his nose in his scalp that smells the oil secretions, that’s his way of reaffirming that’s his child,” he says.

Common reasons people lose their sense of smell, Davidson says, include inflammation caused by nasal polyps associated with allergic rhinitis and a postviral infection that can result from a really bad cold. An injury to either the front or back of the head also can zap a person’s smell by shearing or stretching the olfactory nerves. This can happen with surprisingly little force, says Davidson, and a person doesn’t have to lose consciousness for it to occur.

About 98 percent of cases involving smell loss can be treated through use of antibiotics, steroids or surgery. “When it’s not treatable,” he says, “my job is to explain it, get people to accept it and to make sure they understand the importance of going on rotten-food patrol.” His Web site, www.drdavidson.org, contains a wealth of information for anyone suffering, even occasionally, from nasal disease, including the variety of treatments available. A word of caution from the doctor: Zycam, a zinc-based nasal spray sold over the counter, is under investigation by the Federal Drug Administration following allegations that its use can cause permanent loss of smell. Don’t use it, Davidson advises.

EXPOSURE TO VARIOUS CHEMICALS can damage or destroy the smell sense. More commonly, a variety of environmental pollutants can be downright irritating—provoking that familiar itchy-eye, runny-nose phenomenon. Such is the milieu of the UCSD Chemosensory Perception Laboratory, a research arm of the Nasal Dysfunction Clinic. Tucked away in a back building of an office park off La Jolla Village Drive, the laboratory primarily focuses on how people perceive chemicals and how chemicals exert short-term effects on people.

Visit the lab on any given day and you’re likely to see a stream of volunteer subjects, most of them UCSD students, in a range of experiments using mechanical contraptions to determine levels at which certain chemicals are likely to cause irritation to the eyes, nose or lungs.

“We work to come up with protocols so [chemical manufacturers] can make decisions based on scientific, humanbased exposures,” says lab director Dr. William S. Cain.

Current research under way at the lab, Cain says, includes testing of chloropicrin, heavily used in California for fumigating high-value crops such as strawberries, flowers and tomatoes. In one experiment, a volunteer sits for an hour in a small enclosed chamber in which the chemical is being released; he duly notes every few minutes to what degree his eyes or nose are irritated.

The lab has made a number of important findings in its 10-year history, says Dr. J. Enrique Cometto-Muñiz, a research scientist with the lab. Approaches were developed, for example, to separate the olfactory impact of chemical vapors producing the smell from the chemical-irritation impact of the same vapors producing nose or eye irritation.

“One way in which we did this was by testing people who do not have a functional sense of smell,” explains Cometto-Muñiz. “Anosmics only perceive a chemical in the nose when it begins to produce a ‘feel,’ a sensation such as tingling, piquancy, stinging, irritation, burning, prickling and so on.” The lab also helped to develop an equation that can calculate the odor or irritation potency of a chemical vapor, he says.

Some of the lab’s work has involved “sick building syndrome,” often reported in buildings that have poor ventilation. Symptoms of the syndrome usually are quite general, says Cometto-Muñiz, including fatigue, loss of concentration, headache and irritation of the eyes, nose or throat.

The lab doesn’t study people who report having the syndrome, but it has explored the sensory potency of chemical vapors that come from carpets, cleaning agents and paint.

“We found that almost all of [the above-listed] volatile organic compounds can produce nasal irritation at high enough concentrations,” says Cometto-Muñiz.

A person’s sense of smell generally stays stable until—as with sight and sound—it starts to decline in the late 50s, Cain says. It then becomes increasingly common for a person to recognize a smell but not be able to name it or place it. “It’s called the ‘tip of the nose’ phenomenon,” he says.

In the years he has been researching the sense of smell and irritation, Cain says with a laugh, he’s been asked “thousands of questions” about aromatherapy. “I just say that if a certain smell works for you, then great, use it. But I don’t think there’s any magic in a smell.

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