Loss of Smell

What’s Causing My Loss of Smell and Taste?

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The Smell-Taste Connection

The Smell-Taste Connection

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When your sense of smell goes south, taste usually follows. That’s because the olfactory area in your nose controls both. When you chew food, odor molecules enter the back of your nose. Your taste buds tell you if a food is sweet, sour, bitter, or salty. Your nose figures out the specifics, like if that sweet taste is a grape or an apple. If you plug up your nose, food doesn’t taste the same because you can’t smell it.

Age

Age

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As you age, you lose some of the olfactory nerve fibers in your nose. You have fewer taste buds, and the ones you have left aren’t as sharp, especially over age 60. This often affects your ability to notice salty or sweet tastes first, but don’t add more salt or sugar to your food. That could cause other health issues.

Illness or Infection

Illness or Infection

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Anything that irritates and inflames the inner lining of your nose and makes it feel stuffy, runny, itchy, or drippy can affect your senses of smell and taste. This includes the common cold, sinus infections, allergies, sneezing, congestion, the flu, and COVID-19. In most cases, your senses will return to normal when you feel better. If it’s been a couple of weeks, call your doctor.

Obstructions

Obstructions

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If you can’t get enough air through your nose, your sense of smell suffers. And smell affects taste. Blockages happen if you have nasal polyps. These are noncancerous tumors that grow in the lining of your nose and sinuses. Or you could have a deviated septum that makes one of your nasal passages smaller than the other. Both are treated with nasal sprays, medication, or surgery.

Head Injury

Head Injury

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Your olfactory nerve carries scent information from your nose to your brain. Trauma to the head, neck, or brain can damage that nerve, as well as the lining of your nose, nasal passages, or the parts of your brain that process smell. You may notice it immediately or over time. In some cases, your senses return on their own, especially if the loss was mild to start. You may partly get better and only be able to taste or smell strong flavors and scents.

Certain Medical Conditions

Certain Medical Conditions

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Doctors don’t understand why, but loss of smell can be an early warning sign of dementia, Alzheimer’s, and Parkinson’s disease. Other medical conditions can damage the nerves that lead to the smell center of your brain, too. These include diabetes, Bell’s palsy, Huntington’s disease, Kleinfelter syndrome, multiple sclerosis, Paget’s disease of bone, and Sjogren’s syndrome. If you can’t taste or smell after a few days, talk to your doctor to rule out other conditions.

Cancer and Treatment

Cancer and Treatment

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Certain kinds of cancer and treatment can change the messages between your nose, mouth, and brain. This includes tumors in your head or neck and radiation to those areas. Chemotherapy or targeted therapy and some medications for side effects can also have an effect. You may have a metallic taste in your mouth or find that certain odors are different or stronger. These issues often go away when your treatment ends.

Medication

Medication

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Some prescription and over-the-counter medications can shift your senses, especially antibiotics and blood pressure medications. They either alter your taste receptors, scramble the messages from your taste buds to your brain, or change your saliva. Talk to your doctor before you stop taking any medication.

Vitamin Deficiencies

Vitamin Deficiencies

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Loss of taste and smell could be your body’s way of telling you you’re low in vitamins. Certain conditions and medications can cause you to be low in vitamins associated with smell and taste, like A, B6, B12, and zinc. It can be a chicken-egg situation, too: If you eat less because you can’t smell or taste anything, your body may not get vitamins it needs.

Smoking, Drugs, and Chemicals

Smoking, Drugs, and Chemicals

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Besides its ability to cause cancer, tobacco smoke can injure or kill the cells that help your brain classify smells and taste. Smoking can also cause your body to make more mucus and lessen your number of taste buds. Cocaine use can have a similar effect on your sensory cells. So can hazardous chemicals like chlorine, paint solvents, and formaldehyde.

Diagnosis

Diagnosis

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After a physical exam, your doctor will check your ability to taste and smell separately. For the smell test, you’ll name a series of scents in small capsules or on scratch-and-sniff labels. A taste test involves strips that you identify as sweet, sour, bitter, salty, or umami, also called savory. Your doctor may look inside your nose with an endoscope (a camera on the end of a flexible tube) or order a CT scan for a better view of your sinuses, nose nerves, and brain. 

Complications

Complications

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When you lose your senses of smell and taste, it affects your life in many ways. This condition is a safety risk since you can’t smell smoke, poison, or gas or taste spoiled food. Use fire alarms, check expiration dates on food, and switch to electric if you have natural gas. Always eat healthy food, even if you can’t taste it.

Immune Assault May Explain Loss of Smell in Long Covid

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"We are hopeful that modulating the abnormal immune response or repair processes within the nose of these patients could help to at least partially restore a sense of smell," says Bradley Goldstein. (By Ivan Dudka/Shutterstock)

“We are hopeful that modulating the abnormal immune response or repair processes within the nose of these patients could help to at least partially restore a sense of smell,” says Bradley Goldstein. (By Ivan Dudka/Shutterstock)

An ongoing immune assault on olfactory nerve cells and an associated decline in the number of those cells may explain why some people fail to recover their sense of smell after COVID-19.

The finding, published in the journal Science Translational Medicine, provides an important insight into a vexing problem that has plagued millions who have not fully recovered their sense of smell after COVID-19.

While focusing on the loss smell, the finding also sheds light on the possible underlying causes of other long COVID-19 symptoms—including generalized fatigue, shortness of breath, and brain fog—that similar biological mechanism might trigger.

“One of the first symptoms that has typically been associated with COVID-19 infection is loss of smell,” says senior author Bradley Goldstein, associate professor in the head and neck surgery and communication sciences department and the neurobiology department at Duke University.

“Fortunately, many people who have an altered sense of smell during the acute phase of viral infection will recover smell within the next one to two weeks, but some do not,” Goldstein says. “We need to better understand why this subset of people will go on to have persistent smell loss for months to years after being infected with SARS-CoV2.”

In the study, Goldstein and colleagues analyzed olfactory epithelial samples collected from 24 biopsies, including nine patients suffering from long-term smell loss following COVID-19.

This biopsy-based approach—using sophisticated single-cell analyses in collaboration with Sandeep Datta of Harvard University—revealed widespread infiltration of T-cells engaged in an inflammatory response in the olfactory epithelium, the tissue in the nose where smell nerve cells are located. This unique inflammation process persisted despite the absence of detectable SARS-CoV-2 levels.

Additionally, the number of olfactory sensory neurons were diminished, possibly due to damage of the delicate tissue from the ongoing inflammation.

“The findings are striking,” Goldstein says. “It’s almost resembling a sort of autoimmune-like process in the nose.”

Goldstein says learning what sites are damaged and what cell types are involved is a key step toward beginning to design treatments. He says the researchers were encouraged that neurons appeared to maintain some ability to repair even after the long-term immune onslaught.

“We are hopeful that modulating the abnormal immune response or repair processes within the nose of these patients could help to at least partially restore a sense of smell,” Goldstein says, noting this work is currently underway in his lab.

He says the findings from the study could also inform additional research into other long-COVID-19 symptoms that might be undergoing similar inflammatory processes.

Nasal Cell Damage Linked to COVID Loss of Smell: Study

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Researchers now know why some people recover their loss of smell after COVID-19 and some do not. 

A new study, published Wednesday in the journal Science Translational Medicine, shows that for some people, their body’s immune response becomes dysregulated, even after the virus can no longer be detected by laboratory tests. Specifically, COVID-19 can cause a prolonged and damaging inflammatory assault on nerve cells in the nose that are responsible for the sense of smell.

The study was small, with samples from 24 people split into three groups: people with post-COVID prolonged loss of smell, people with a normal sense of smell after recovering from the virus, and people who never had COVID and who had a normal sense of smell. 

“The findings are striking,” researcher Bradley Goldstein, MD, PhD, an associate professor at Duke University School of Medicine in North Carolina, said in a news release. “It’s almost resembling a sort of autoimmune-like process in the nose.”

Persistent loss of smell after COVID-19 can last years. The good news is that even patients most affected by the virus appeared to maintain the cell types needed to repair the sense of smell, the study found.

Goldstein said the findings point scientists toward treatments that “could help to at least partially restore a sense of smell.” 

He said his lab at Duke is trying to help develop those treatments. 

While the researchers set out to study what caused the prolonged loss of smell after COVID-19, their findings may also shed light on other symptoms of long COVID, they said.