Houston ENT and Allergy Blog

Anosmia (Loss of Sense of Smell) and COVID-19

By:
John D Edwards, MD
January 29, 2021

anosmia loss of smell covid19 (1)Loss of smell, or anosmia, is one of COVID-19's known symptoms. But, if you're experiencing anosmia, you don't need to panic. There are a lot of possible causes for anosmia and most are temporary. Below you'll find an overview of how you smell, what anosmia is and its causes, how to diagnose and treat it, and how it relates to COVID-19.

How We Smell

When a smelly object, such as a flower, releases a molecule, it stimulates certain nerve cells in your nose called olfactory cells. These nerve cells then send scent information to your brain, which then interprets and identifies the smell. 

If you didn't have a sense of smell, your taste would also be impacted since your taste buds can only detect only a few flavors by themselves. 

 

What Is Anosmia - Definition of Anosmia

Anosmia is the term used for the total loss of sense of smell. If you didn't have your sense of smell any food you ate would taste different, you wouldn't be able to smell different scents (like that of a flower). 

Without a sense of smell, you also may possibly find yourself in unknowingly dangerous or harmful situations. For instance, without the ability to detect certain odors, you wouldn't be able to smell:

  • Smoke from a fire
  • A gas leak
  • Sour milk

Individuals with anosmia might lose interest in food and even in eating altogether, which could lead to malnutrition and loss of weight.

 

What Are the Causes of Anosmia? 

Anosmia is often caused by a blockage or swelling in your nose that keeps smells from getting to the top of your nose. It's sometimes caused by an issue with the system responsible for sending signals to your brain from your nose.

The primary causes of anosmia are:

1. Irritation to Your Nose's Mucous Membranes

This can be due to:

  • Smoking
  • Sinus infections
  • Influenza or the flu
  • Common colds
  • Allergic rhinitis (allergies)
  • Nonallergic rhinitis (chronic congestion not due to allergies)

The most common cause of you temporarily losing your sense of smell is a cold. In these cases, the anosmia typically goes away by itself.

2. A Blockage in Your Nasal Passages 

Anosmia can occur if something is blocking air passage to your nose physically. This might include:

  • Nasal polyps
  • Tumors
  • A nasal septum or bone deformities inside your nose

3. Nerve or Brain Damage

You have receptors inside your nose that send your brain information through your nerves. Anosmia can occur if there's damage to any part of this pathway. This damage can occur from many conditions, such as:

  • Alzheimer's disease
  • Old age
  • Hormonal problems
  • Brain tumors
  • Diabetes
  • Underactive thyroid
  • Huntington's disease
  • Epilepsy
  • Parkinson's disease
  • Multiple sclerosis
  • Schizophrenia
  • Medications (i.e. some high blood pressure medications and antibiotics)
  • Brain surgery
  • Exposure to chemicals that burn your nose's insides
  • Stroke
  • Radiation therapy
  • Long-term alcoholism
  • Vitamin deficiencies and malnutrition
  • Head or brain injury

There are also rare cases where individuals are born with a genetic condition that causes them to have no sense of smell (congenital anosmia).

 


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How Is Anosmia Diagnosed? 

If you experience loss of smell you can’t attribute to an allergy or cold that persists over a week, make an appointment with an ENT specialist. They’ll take a look inside your nose using a special tool to see if there’s an infection or obstruction present.

It can be difficult to measure the loss of smell. The doctor might ask you some questions about any existing symptoms you're experiencing, give you a physical exam and inquire about your health history.

They might ask when the issue began, if all types of odors are impacted or just some and if you can taste food or not. Depending on how you answer, they might also perform any one or more of the following tests:

  • X-ray of the skull
  • CT scans 
  • Nasal endoscopy to view the inside of your nose
  • MRI scans

 

What Are the Treatments for Anosmia? 

There are certain treatments for anosmia, including:

  1. Antibiotics: If the doctor believes there's an infection causing your anosmia, they might prescribe antibiotics to fight the infection. 
  2. Smoking cessation: Your doctor will suggest you stop smoking if you smoke, which can negatively impact your ability to taste and smell.
  3. Supplements or vitamins: Certain medical conditions can cause anosmia. The doctor might recommend certain vitamins or supplements or recommend you make an appointment with a specialist.
  4. Dental hygiene: Inflammation of the gums or gingivitis can impact your ability to taste normally. You'll have to address any dental issues and work on improving your dental hygiene habits.
  5. Medication assessment: If you use certain medicines regularly, like the antidepressant amitriptyline or antihistamines, you might have a decreased ability to smell or taste. The doctor might assess how these medicines you're currently taking could be impacting your senses of smell or taste.
  6. Sinusitis and surgery: Sinusitis could impact your sense of smell. Also, any previous radiation therapy you've had to your nasal passages or throat, surgery in your nose or chemotherapy could permanently or temporarily impact your sense of smell.

 

Loss of Smell - Precautions to Take

Individuals with anosmia should be extra cautious about their home's smoke alarms functioning properly. They also need to be cautious about where they store food and the use of natural gas since they might not be able to detect if the food has spoiled or if there's a gas leak.

Some precautions you might want to take if you have anosmia are:

  • Reading labels on chemicals such as insecticides and kitchen cleaners
  • Labeling foods properly that have expiration dates
  • Using electric appliances

 

How COVID-19 Can Cause Anosmia 

In some COVID-19 cases, anosmia has become a hallmark symptom. Experts are now learning how anosmia might reveal whether an individual is likely to have a serious case.

Around 86% of individuals with COVID-19 lose some or all of their sense of smell. But most who lose it (about 55%) experienced a mild form of COVID-19, according to some newly published research.

Researchers aren't quite sure of the reason for this, however, they believe those with mild illness might have a greater level of specific antibodies that limit how COVID-19 spreads to the nose. But, there's no definitive answer. What they do know is the loss of smell in COVID-19 is more than just the loss of smell you see with seasonal colds and upper respiratory infections where the common runny nose and nasal congestion symptoms lead to poor airflow and decreased odor delivery to the nose's region that's responsible for the smell.

Most COVID-19 patients do experience a certain level of anosmia, usually temporary. Electronic health record analysis shows individuals with COVID-19 are 27 times more likely to experience anosmia but are only about 2.2 to 2.6 times more likely to experience cough, fever, or respiratory trouble, compared to individuals without COVID-19. 

Certain studies hint at COVID-19-related anosmia being different from anosmia other viral infections cause, including other types of coronaviruses. For instance, individuals with COVID 19 usually get their sense of smell back after a few weeks, much quicker than the months it takes to recover from the loss of smell related to a subset of viral infections that often damage olfactory sensory neurons directly. 

Also, other viruses cause temporary anosmia by triggering upper respiratory problems like a stuffy nose. Certain people with COVID-19, however, still experience anosmia, even without nasal obstruction. 

 

Contact Houston ENT & Allergy

If you're experiencing anosmia, you may need to see one of Houston ENT & Allergy Services  Ear, Nose, and Throat (ENT) doctors or otolaryngologists to determine the cause. Request your appointment today. 

 

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