WSJournal. Uncork the Nose's Secret Powers

Sense of Smell Drops With Age, but Don't Despair: There Are Ways to Sharpen Your Sniffer at Home

How sweet it is to smell. The nose is a hardworking organ, with powers much greater than most people realize. A keen sense of smell offers more flavors, more safety, even more happiness.

But be warned—human olfactory powers degrade as the years go by, resulting in a detectable loss by the time many people reach their 30s. Gradually, it can deteriorate to the point where people are unable to notice the odor of rancid food or a household gas leak.

The good news: There are exercises you can do at home to protect and even sharpen your sense of smell. "Someone who is colorblind can look at red and green all day but never see it," says Alan Hirsch, director of the Smell & Taste Treatment & Research Foundation, in Chicago. "But with smell, you can actually cause nerve connections to act, and smell what perhaps you couldn't before."

Smelling is one of those things a person may not fully appreciate until it's gone. Patrick Collins, a 62-year-old retiree of the Chicago police force who lives in Sharon, Wis., has been adjusting to life without scent ever since the bad cold he had four years ago. When it disappeared he realized his sense of smell had disappeared, too, a relatively uncommon effect. Doctors told him the cold virus had caused nerve damage.

Mr. Collins put in a gas-leak detector and consults his wife before eating leftovers. Even the time he spends with his 4-month-old granddaughter is affected. "You know that baby smell?" he says. "I can't smell it."

A loss in ability to smell usually brings some loss in taste. Both senses contribute to perceived flavor. "When we chew and swallow, volatile molecules from the food go through the rear of the nasal cavity to the olfactory receptors in the roof of the nose," says Richard Doty, director of the University of Pennsylvania's Smell and Taste Center. "If you hold your nose and put chocolate in your mouth, you won't taste the chocolate."

Upper respiratory infections, pollution, head trauma and diseases including diabetes all have the potential to compromise our sense of smell. Sometimes the problem is temporary, the result of an environmental insult like cigarette smoke or chemical fumes.

More insidious, though, is time. Just as eyesight and hearing fade with age, so too does the sense of smell, experts say. By age 60, about half of people will experience a reduction in their ability to smell, and by age 80, about three-fourths will, Dr. Hirsch says. The Smell & Taste Treatment & Research Foundation is a 25-year-old organization that sees patients and conducts research of its own as well as for the pharmaceutical and consumer-product industries.

From 3 million to 4 million Americans have been diagnosed with conditions such as anosmia, the complete inability to smell, and hyposmia, a reduced capacity, Dr. Hirsch estimates. These numbers are expected to rise sharply as baby boomers age.

It's a golden opportunity for companies to sell products with more-noticeable, pungent scents to cater to baby boomers' flagging noses. But while some companies use unusual botanical fragrances to distinguish their products, they aren't turning up the volume.

"There's a tremendous opportunity right now and they're missing it," says Thom Blischok, chief retail strategist at consulting firm Booz & Co. "More consumer-product manufacturers need to find a way to have aging consumers enjoy the flavors and fragrances of their products."

Until then, there are simple at-home exercises that perfumers and other professional "smellers" recommend to keep the sense of smell in shape. Some can help detect a deficit worth medical attention.

Dr. Hirsch suggests these tests: Close your eyes and taste a little vanilla and chocolate ice cream. "If you can't taste the difference, you may have a problem," he says. Or hold a pad soaked in rubbing alcohol just beyond your chin. If you can smell it, your sense of smell is probably fine.

Ron Winnegrad, director of International Flavors & Fragrances Inc.'s IFF +0.15% New York perfumery school, teaches aspiring perfumers the basics of perfume skills. His first rule of thumb: Be scent-conscious in your day-to-day life. "If you're drinking a cup of coffee or tea, actually smell it before you drink it, and when eating food, smell it first." he says. "If you do this on a regular basis, you will increase your sense of smell."

With his students, Mr. Winnegrad uses drills that involve smelling vials of raw materials over and over again until identification becomes ingrained. Many of the fragrances he uses can be found in a home kitchen, including clove, cinnamon, nutmeg, vanilla, celery and carrots. Pencil shavings can provide a cedar note. A leaf broken off a house plant can provide a green, herbal note.

Mr. Winnegrad suggests keeping each ingredient in a separate small jar and smelling the collection once a day for about a half-hour. Rather than take one deep sniff, take two or three short inhalations and then exhale. "That way you will avoid nose fatigue," he says.

Scott Carney, master sommelier and director of wine education at the International Culinary Center based in New York, teaches students to visualize the scent notes found in wine. If someone is struggling to identify an individual note—say, guava—he will send the student to the grocery-store produce aisle to find a guava. "Go smell it," Mr. Carney will say. "See what you can invoke when smells come close to that one again."

"Everyone will have a slightly different interpretation," Mr. Carney says, "but at the end of the day you've made sense of what it smells like to you."

To help train the brain to discern differences among scents, Dr. Hirsch recommends what he calls "sniff therapy." Choose three or four different types of scents that you find pleasant—say, a floral scent, such as those found in shampoo or soap; a fruity scent from berries, a banana or some other resilient fruit; and another, different scent, like coffee. Avoid irritating scents like onion or ammonia, which can hamper smelling ability, he says.

Sniffing these scents frequently, around four to six times each day, will eventually spark different receptors in the nose to work.

Though smelling food isn't a survival skill anymore, it still serves a biological purpose. "It's a first-warning system that we have for danger," says Pamela Dalton, faculty member at Monell Chemical Senses Center, a scientific-research institution. It may warm up the digestion process, she says. "It may in fact make us digest and metabolize our food more efficiently."

Caryl Sheehan, a 53-year-old geologist in Sacramento, Calif., can't remember a time when she could smell. She has drunk more than her fair share of sour milk, and she is stumped when she hears something "smells like Christmas." Under clinical treatment and taking medication (Cerefolin with NAC), she is discovering the scent of cut grass and coffee. "For the first time ever I took the garbage out because it smelled bad," she says. "Usually I just wait until it's full."

Mr. Collins began clinical treatment last year (he is taking medications including pentoxifylline). He is encouraged by flashes of scent he sometimes gets when he yawns. Although he has little ability to taste, he continues to eat pizza, chocolate and grilled steak and drink Starbucks SBUX +0.21% coffee. "In a way I'm tricking myself into thinking that I can taste it and am trying to get as much enjoyment out of it that I can," he says. "I never give up hope."