Vision and hearing are senses that guide us through the world. And you can see how people who have lost one of them are more prone to accidents. Now a group of nose doctors are raising a stink about a more subtle hazard -- the inability to smell. These otolaryngologists, at Virginia Commonwealth University, poked through records of 445 patients seen at the university's clinic for smell and taste disorders between 1983 and 2001, and correlated rates of certain accidents with olfactory deficits.

As expected, those accidents were more common among those who did not have a nose for trouble. Indeed, 37 percent of the patients had at least one "olfactory related hazardous event" -- charring their stews or eating spoiled leftovers, compared to 19 percent of patients with normal nasal acuity also seen at the clinic.

Forty-five percent of the problems occurred in the kitchen: burning food -- or igniting it on the stove.

Twenty-five percent of the events involved eating spoiled food, and 23 percent, a failure to smell a natural-gas leak. Seven percent were attributed to failure to smell a fire (patients could report more than one hazardous event).

Whose nose knows?
And while you might say those results were right under our noses, putting numbers on the risk makes the issue more pungent for doctors and patients alike. "Certainly it's intuitive that the loss of a sense of smell might put you at risk for some of the things that we studied," says study co-author Evan Reiter, an otolaryngologist and head and neck surgeon at Virginia Commonwealth University. "We felt it was important to show that, and to get the word out, first, among physicians, so they will be more apt to counsel patients, and second, in the lay press, so patients will be more aware, for safety, and for reassurance."

Researchers estimate that 2.7 million Americans have some deficiency with their smelling system -- and roughly 20 to 25 percent of those people have a complete loss. The sense of smell, like vision and hearing, can waft away through normal aging. Dozens of medicines may affect smell, Reiter says, including some anti-cancer agents, antibiotics, and cholesterol-lowering drugs.

But a sudden loss can also result from a viral attack on the one thousand-odd types of scent receptor in the nose. "When you have a bad cold, have gotten really congested, your sense of smell disappears," Reiter says. "Normally after the viral infection and congestion go away, the sense of smell returns. But if the virus has done damage, the infection goes away and you feel normal, but you still can't smell."

The nerve connecting the snout to the brain can be damaged in motor vehicle accidents, even low-speed crashes. Rapid deceleration can shift the brain in the skull, Reiter says. "The small nerve fibers that go from the nose through small holes in the base of the skull are injured. The holes in the bone have a shearing effect." Although the nerves often regenerate, they rarely find their way from the brain all the way back to the sniffer.

Indeed, the permanence of many olfactory problems frustrates many doctors, who prefer to treat treatable problems. But if it's seldom possible to restore smell, it's usually possible to reduce the harm. And Reiter would like to lead more doctors, yes, by the nose, to counsel patients about safety:

Date your leftovers before burying them in the back of the refrigerator.

Ask friends or relatives to smell questionable food before you chow down.

Use smoke detectors. Check their batteries. Press the test button monthly.

We just hope that advice won't put the doctors' noses out of joint...

-- David Tenenbaum

Bibliography
Hazardous Events Associated with Impaired Olfactory Function, Daniel Santos et al, Archives of Otolaryngology and Head and Neck Surgery, March, 2004.