When the Nose Doesn’t Know

As every pet parent knows, simply opening a can of food brings Fido or Fluffy on the run.

It’s not the popping sound that gets them going. It’s the scent hitting their vomeronasal organ (VMO), two structures pinned to the lining of the nose or the roof of the mouth that may hold as many as 300 million olfactory receptors along with nerves that send fibers straight to the brain which decodes the odor messages.

For a whole list of animals from snakes to pigs and primates, the VMO translates the world into sensed images. Millennia ago, when we humans began to rely on the sense of sight as our most important way to “see” things, our VMO started to shrink. Today, it’s just about a measly 5 million or so receptors with practically none of those brain nerve connectors.

But that doesn’t mean our sense of smell is dead. In fact it’s still intimately connected to our sense of taste. Bite into something tasty, chew, and odor molecules migrate to the back of your nose to tell you if what you’re eating is sweet, sour, bitter, or salty. Damage those nasal sensory nerves and all food is, well, tasteless.

That can happen if you get hit on your head. Or if you’re taking certain prescription drugs such as antihistamines or meds to control your blood pressure. Or more prosaically, if you have a cold, an allergy, a sinus infection or the flu. Absent all that trouble, some experts suggest that a sudden or gradual waning of the sense of smell may be warning of oncoming dementia. Right now, though, the latest proof of the smell/taste connection is, yes, indeed, COVID.

Nerve Samples

None of us is going to get younger, but ordinarily, the ability to smell things returns when the physical infection resolves, but for some COVID patients the loss lingers longer. Thanks to a new study from Duke, Harvard and the University of California-San Diego, doctors now have a have a clue as to why.

After analyzing nerve samples collected in from 24 biopsies, including nine patients whose COVID erased their sense of smell, the study’s senior author Bradley Goldstein, Associate Professor in Duke’s Department of Head and Neck Surgery and Communication Sciences, reported finding inflammation in the tissues hosting smell nerve cells lingering even after COVID was no longer detectable. Perhaps, he says, the same cellular assault may account for other long COVID symptoms such as fatigue, shortness of breath and, to use the scientist’ technical term, “brain fog.”

Finally: Fair warning, we all lose olfactory nerves and taste buds as we age, with 60 being a possible point of demarcation. But at any age, if your ability to smell the world around goes awry, check with your doctor who can run a “smell test” with scratch and sniff scents and a taste test with test strips for sweet, sour, bitter, salty, and umami (savory). The tests are worth your time because your senses of smell and taste are not just sitting there for pleasure. They are also protective tools enabling you to smell, smoke, poison, and gas plus detect spoiled food.

Now go feed Fido and Fluffy who’ve waited patiently as you read this.