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This removal may involve a procedure to remove nasal polyps, straighten the nasal septum, or clear out the sinuses. People with a partial loss of their sense of smell can add concentrated flavoring agents to food to improve their enjoyment. A well-functioning sense of smell is something most people take for granted, until it's lost. Losing your sense of smell, known as anosmia, can make…. Loss of smell can occur due to problems in the nose, brain, or nervous system. The impairment is usually a distorted sense of smell. Impaired taste is the absence or altered sense so taste, such as having a metallic taste in the mouth.

Most people only experience impaired taste…. A metallic taste in your mouth is a type of taste disorder. The unpleasant taste can develop suddenly or over longer periods of time.

There are many…. Learn about hyperosmia, a heightened sense of smell, and its causes. Rhinitis is an inflammation of the inside of your nose. It can be allergic or nonallergic. Learn about common triggers, such as pollen and pet dander…. Learn about cacosmia, including what can cause it and whether it's treatable.

Collagen is an essential building block for the entire body, from skin to gut, and more. Here's five changes you may see or feel just by taking more…. You can do a lot of prep work to make the perfect sleep environment. But if that doesn't work, here are 6 other hacks to try. Identifying your triggers can take some time and self-reflection.

In the meantime, there are things you can try to help calm or quiet your anxiety…. What Is Anosmia? Causes Diagnosis Complications Treatment Overview. What causes anosmia? How is anosmia diagnosed? What are the complications of anosmia? How is anosmia treated? Impaired Smell. Impaired Taste. When the receptors interact with molecules, they set off a chain reaction that ends by sending a message to our brains. As for the precise nature of those interactions, Buck and Axel could only theorize.

They posited a sort of lock-and-key relationship between the olfactory receptors in our noses and the molecules in the air.

But the number of receptors they discovered instantly posed a mathematical problem. Humans have about kinds of olfactory receptors far fewer than mice , but we can smell about 10, distinct odors. So Buck and Axel theorized that smell was combinatorial. Each receptor, their research showed, is uniquely primed to react to a few different molecules, and our noses sense distinct odors when many receptors fire at the same time. John Kauer, then a researcher at Tufts University, relates the idea to playing chords on a piano.

Inspired by Buck and Axel, who won the Nobel Prize in for their work, Mershin and other scientists conceived of odors as simply lists of molecules. If you want to understand the smell of a clove of garlic, the thinking went, the answer lies in its chemical components. The agency funded scientists across the country to build a bunch of would-be sniffing machines and then brought them to a field in Missouri for testing.

Anosmia: Causes, Complications, and Treatment

The ground was sown with every manner of land mine, from small antipersonnel devices the size of tuna fish tins to hefty antitank munitions. Although stepping on the mines could no longer set them off—the fuses had been removed—the buried explosive ordnance could still be set off by, say, a lightning strike. Kauer had built a gray, shoebox-sized device that he eventually christened the ScenTrak. Instead, it was packed with long strands of molecules called polymers that Kauer knew would react to DNT, a molecule common in most land mines.

ScenTrak was able to pick out nearby traces of DNT in the air of an otherwise odorless lab. Out in the field, though, when Kauer scanned the ScenTrak back and forth over a patch of ground, it became confused. The polymers would react to DNT, but also to the weather, to plants, or to certain kinds of soil.

The Quest to Make a Bot That Can Smell as Well as a Dog

Other devices in the competition, including one called Fido and another called Cyranose, were based on roughly the same theory. They all used polymers sensitive to specific compounds. And they all proved somewhat narrowly functional. Fido is now used at military checkpoints to scan for explosives at close range. They often misfire in scent-rich environments where odors—apparently made of some of the same compounds—may waft in from various nonexplosive sources. Today, most scientists believe that the lock-and-key theory of olfactory bonding is far too simple.

In some cases, it turns out, molecules with very similar shapes have completely different odors; in others, very differently shaped compounds smell alike. Instead, many receptors bind to many different molecules and vice versa. Mershin and Zhang are an odd yet harmonious pair. Mershin rarely takes the same path twice.

What Is Anosmia?

Sometimes he will forget his own address. He is also insatiably, compulsively curious. He once devised a game for his children that involved having them soak a cotton ball in perfume, blindfold themselves, and then try to find the cotton ball after it had been hidden.

In addition to noses, he is building houses in Namibia out of mushrooms and working with a postdoctoral fellow on ways to remove heavy metals from water. Zhang is that person. Where Mershin is restless, Zhang, who runs his own research group called the Laboratory of Molecular Architecture, is deliberate and slow. He believes you have to go deep on one project, one question.

Are they in fact binding with molecules? Do other factors like humidity or other compounds affect how those receptors respond? No one knows. Zhang wanted to change that—by figuring out some way to see an olfactory receptor. Each receptor is shaped like a long string that winds back and forth through the thin membrane that separates a cell from the outside world.

And if the receptor is tilted or upside down? About half of any olfactory receptor sits outside the cell, ready to interact with molecules. Then a middle section sits inside the cell membrane, and the rest resides inside the cell. When the exterior part of the receptor binds to a molecule, it changes shape, and the cell sends a message to your brain. While the heads and tails of an olfactory receptor—the parts that sit inside and outside the cell—love water, its middle section is hydrophobic, like the cell membrane that encases it.

That means that when you take the receptors out of a cell and put them in water, they tend to clump together instead of dissolving, which makes them nearly impossible to isolate and work with. Zhang has been toiling away at his goal since At one point, he spent eight years simply trying to create water-soluble receptors. Nor has anyone else. They are simply too small. Spurred by the wars in Iraq and Afghanistan, RealNose had a new mission and a new sense of urgency.

Instead of searching for land mines, the mechanical noses needed to be able to identify IEDs, which were laying waste to American troops. They had to use mammalian olfactory receptors as their sensors. Zhang had a big advantage over other scientists competing for those Darpa grants. Thanks to his work, he had one of the only labs in the world that had experience growing olfactory receptors in embryonic cells and then working with them in the lab.

Why did they need to use the actual, biological structure when it would be easier to use something synthetic? Mershin and Zhang decided they would grow a bunch of olfactory receptors in their lab and then essentially smear them onto a circuit board. Then they would connect the circuit boards to an electrical current. When the receptors interacted with volatile compounds, they would change their shape, just like they do in a regular nose. But instead of sending a message to a brain, the interaction would be recorded as a simple blip in electrical current.

On a clear day in early spring, Mershin leads me into his lab and rifles through some cardboard boxes and equipment until he unearths a container of old artificial nose prototypes. In one hand, he pulls out a plastic bottle with two metal nozzles haphazardly held in place with epoxy.

From his other hand, a thin plastic chip dangles from some electrical wires.

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It was a failure. The receptors seemed to work, but the bottle was too big; smells would linger too long for the scientists to get a clear reading. From his hopper of prototypes, Mershin eventually pulls out the device, called the Nano-Nose, that he and Zhang ultimately submitted to Darpa.

The whole contraption is about the size of an extra-large roasting pan and is emblazoned with the words "Property of the US Federal Government. After all their prototypes, they had eventually homed in on a design that used an array of eight circuit boards, each about the size of a credit card. Inside that bulletproof metal housing, each board sat in a separate airtight bay, capable of receiving its own puff of odor and responding with its own electrical pattern.

Smells could be sent into the box, and directed to each board, by an air pump that mimics taking a deep sniff. He even brought their own odor delivery system: a modified inkjet printer called the StinkJet. Mershin had originally envisioned putting a supercomputer underneath the Nano-Nose that would dig through databases listing thousands of compounds and print out those the nose registered.

Instead, they resorted to what Mershin thought of as a hack. Darpa had given them a list of odorants that their machine would be asked to recognize. Then, in the actual test, they would sample each mystery odorant eight times—once through each of the eight bays—and run it through a gauntlet of varying electrical conditions. This amounted to a process of elimination, meant to help the pattern-matching algorithm filter out false positives.

The Darpa tests were highly controlled. During lunch breaks, the team would rush the nose back to their hotel room, soldering pieces onto it to keep improving it while ordering room service. In the end, the mad dash paid off.


The Nano-Nose passed the sniff-off and was able to sense isolated odors in the lab. It even beat dogs in a controlled environment, sniffing out odors in lower concentrations than canines could detect. In fact, Mershin says, the Nano-Nose was better without it. To him, the project revealed a fundamentally important aspect of olfaction: Our noses are not analytical tools. Conversely, if we narrow our attention on the signals our receptors are sending, we can pick out the subtle scent of shallots or fennel in a pasta sauce brimming with the competing scents of tomato, peppers, and garlic.

He needed to know what something smelled like, not what it was made of, and those are fundamentally different things.

You STINK! 6 Reasons You Smell BAD (And May Not Even Know It)

On a warm Sunday in September, I go searching for bones with a German shepherd named Kato, who has been trained to find human remains. Kato and his owner, Peggy Thompson, volunteer with law enforcement agencies. They help look for lost hikers, wildfire casualties, and victims of crimes. Out of her garage she pulls a bag of bones, a jar of teeth, and some bloody gauze. It smells musty and human in an inexplicable but unsettling way. We scatter a few bones and teeth across her gravel driveway, under some bushes, and on the lawn.

She wedges the skin into the knot of a small tree. He weaves his way back and forth, moving deliberately, nose to the ground. He finds the skin within five minutes.

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The rest of the bones and teeth take another 10 at most. Waggoner, who also has his own patented training program for detection dogs, argues that machines break down early in the smelling process. Dogs inhale and exhale about five times every second, through nostrils that route the intake and outward flow of breath through different channels. All that snorting creates a pressure differential—a kind of smell vortex—that helps them pull a rich, new sample into their nose with each sniff. Well, no one knows. Still, dogs are not perfect sniffers themselves. On a second visit with Thompson, I watched another dog, a 3-year-old Malinois named Annie, completely lose focus on tracking down a bone when she encountered several pigs in a nearby field.

Dogs get frustrated and tired.