Anosmia

Anosmia is a complete loss of the smell sensation. It can be a sign of certain medical conditions, such as head trauma, and it also is a symptom of COVID-19.

The most common side effect of anosmia is a lack of appetite, but it can lead to dangerous consequences too if you can’t smell things like smoke, toxic fumes, or rotting food. Anosmia can be permanent if it’s caused by nerve damage. It usually improves when it’s caused by an infection.

Research shows that anosmia afflicts about 3.2% of U.S. adults who are age 40 and older. This article will discuss the symptoms of anosmia, causes, risk factors, complications, diagnosis, and treatment.

Symptoms of Anosmia

Anosmia can be distressing but isn't very noticeable to many people. If you have anosmia, you might occasionally notice that you can't smell things you normally used to be able to smell. For example, others might comment on a bad odor or a pleasant scent you don't detect. 

Many people with anosmia also have a decreased appetite and less enjoyment of food. This can be the first sign that something's wrong. 

Types of Anosmia

While anosmia is defined as a total loss of the sense of smell, there are other abnormalities of smell sensation, including:

• Hyperosmia: Increased sense of smell, common with migraines and during pregnancy
• Hyposmia: Diminished sense of smell 
• Parosmia: An altered sense of smell, where odors don’t smell like they should 
• Phantosmia: Perceiving scents that are not there

You can have more than one of these problems. For example, if you have anosmia and phantosmia, you would not be able to detect odors around you, but you might incorrectly perceive a scent that isn’t present. 

Causes of Anosmia

Most of the time, anosmia is caused by nasal congestion that blocks the detection of odors. This is usually reversible if the congestion improves. It is also very common to lose some sense of smell with age. 

The sense of smell is controlled by the olfactory nerve, also known as cranial nerve 1. Anosmia can occur if there’s damage to this nerve or if there’s damage to the areas of the brain that register your perception of odors.

Some common causes of anosmia include:

• Congestion from an upper respiratory infection (a cold) or sinus infection
• Nasal inflammation due to allergies 
• Nasal polyps, which are benign (noncancerous) growths in the nasal passages
• Exposure to inhaled or ingested fumes or toxins, such as paint or medication
• Head trauma damaging the cranial nerves 
• COVID-19, which is believed to damage the olfactory nerve 
• Neurodegenerative diseases, including Alzheimer’s disease and Parkinson’s disease 
• A tumor in the nasopharyngeal region (the area behind the nose and the upper back of the throat)
• Inhaled cocaine use 

Most of the time, anosmia from inflammation will resolve after the inflammation subsides. People who have nerve damage might have permanent anosmia.

Some people who have recovered from COVID-19 infection continue to have anosmia for months or longer. Since this is a relatively new virus, the long-term outcome regarding recovery from anosmia in COVID-19 is not definitively known.

What Medications Can Cause Anosmia? 

Many medications can affect your sense of smell. There are various ways that medications can alter smell sensation, such as altering chemical signals, slowing nerve activity, damaging the olfactory nerve, and damaging the lining of the nasal passages.

Just a few examples of medications that can affect your sense of smell include:

• Aspirin
• Advil, Motrin (ibuprofen)
• Tylenol (acetaminophen)
• Moxatag (amoxicillin)
• Norvasc (amlodipine)
• Insulin
• Elavil (amitriptyline)
• Xanax (alprazolam)

In general, medications associated with altered smell sensation might not always specifically cause anosmia—they could also cause other changes, such as hyposmia.

Most people who take these medications do not experience any change in smell sensation. However, if you start to notice that your sense of smell is changing, it could be related to medication that you're taking.

Complications and Risk Factors Associated With Anosmia

If you have lost your sense of smell, it can cause some annoying issues and may also lead to dangerous consequences. 

The sense of smell can enhance the enjoyment of the environment—including nature, flowers, and perfumes. People who have anosmia miss out on these pleasant experiences. This can be frustrating, and it takes away potential enjoyment in life.

Not having smell sensation can also interfere with some practical day-to-day tasks at home or at work. For example, your sense of smell can no longer detect if a food is done cooking, or if paint has dried. 

Dangers of Anosmia

Serious issues can arise due to anosmia. And if you have this condition, you must take precautions to avoid running into harmful problems. 

Potential harms include not being able to smell:

• Your child's soiled diaper
• When something is burning 
• Smoke 
• Toxic chemicals 
• Leaking fluids, such as gasoline 
• Rotting food before you or your child eats it 
• Something rotting in the home or trash that is overdue to be taken out 
• An infection affecting your pet

If you have anosmia, you need to be extra cautious to look for these things or to ask other people to alert you to a bad smell. Depending on the situation, you might also consider getting a device to alert you of smoke or fluid leaks in the home. 

How to Treat Anosmia

Often, anosmia improves on its own once nasal congestion resolves. You may be able to get treatment to improve your lost sense of smell if it’s been affected by inflammation or a polyp. But there is no specific medical or surgical intervention that enhances the sense of smell. 

Treatments for causes of anosmia can include:

• Decongestant for nasal inflammation 
• Surgical removal of a polyp or cancerous growth 
• Surgical repair of a facial fracture that could be placing pressure on the olfactory nerve 
• Discontinuing medications, exposure to toxins, or cocaine to potentially allow the area to heal, which might restore some sense of smell 

Are There Tests to Diagnose the Cause of Anosmia? 

You can test yourself to determine whether you have a decreased sense of smell by sniffing an item, deciding whether it smells as it should, and asking someone else if they can smell it. It can be hard to know for sure sometimes, especially because you are likely to have an expectation of what things should smell like. 

A healthcare provider would test for anosmia by bringing an item near your nose—such as rubbing alcohol—and asking you what it smells like. They would ask about your symptoms and medical history during an anosmia evaluation.

Your physical examination would identify other associated problems. For example, if you have respiratory allergies, you might have wheezing. And if you’ve had head trauma, you could have other signs of trauma, such as bruising. You may also have diagnostic testing to establish whether you have certain medical issues. 

Examples of testing you may need include:

• COVID-19 test
• Chest X-ray 
• Sputum sample (coughed-up material)
• X-ray of facial bones 
• Brain imaging, such as computerized tomography (CT) or magnetic resonance imaging (MRI)

Once the cause of your anosmia is diagnosed, your healthcare provider will discuss your treatment plan and prognosis with you. 

When to See a Healthcare Provider 

If you notice that you’ve lost your sense of smell or that you are developing changes in your smell sensation, you should see a healthcare provider about it. Since anosmia can occur with dementia and Parkinson’s disease, you should tell your healthcare provider if you or a loved one has this symptom, rather than ignoring it.

Summary 

Anosmia is a complete loss of smell sensation. There are many causes, including a cold, allergies, COVID-19, head trauma, nasal polyps, neurodegenerative disorders, and damage to the nasal passages.

Smell sensation often returns to normal after a cold, but when it’s caused by nerve damage or another type of damage, it might be permanent or may only partially return with treatment. It’s important to have a medical evaluation so the cause can be treated. 

A Word From Verywell 

When loss of smell sensation happens as a temporary effect of nasal congestion, it can be annoying. Sometimes regaining your sense of smell can be a welcome sign that your cold or allergy is improving.

Anosmia can also be a consequence of brain damage and degenerative neurological diseases. In these instances, it’s important to work with your healthcare providers on maintaining adequate nutrition, because a decreased appetite and weight loss are common consequences of being unable to smell odors.