What Is Parosmia and How Long Does it Last?

Medically Reviewed By Darragh O'Carroll, MD
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Parosmia refers to a distorted sense of smell. It can cause you to perceive scents differently, such as a familiar smell to seem changed, or a pleasant smell to seem foul. Common causes include head injury, chemical exposure, and infections such as COVID-19. Parosmia differs from anosmia, which is the loss of smell, and phantosmia. Phantosmia causes you to perceive unpleasant smells when there is no scent present. Instead, parosmia occurs when there is a change to the way your brain perceives existing smells.

Treatments for parosmia focus on healing the olfactory bulb. This is the neural structure in your nasal cavity that helps you detect smells.

This article explains parosmia, its causes, complications, and treatments. It also discusses parosmia’s link to the novel coronavirus as well as some frequently asked questions.

Signs and symptoms of parosmia

A woman leans down to smell growing flowers.
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Symptoms of parosmia and their severity may vary slightly in each person.

The main symptom of parosmia is a change in the way you perceive smells. For example, things that previously smelled pleasant may now smell foul.

You may also experience lowered scent perception. This means it may be more difficult to notice or recognize certain scents around you. Conversely, some smells may become overpowering.

If parosmia causes certain foods to smell unpleasant, it may lead to nausea or a feeling of sickness after eating. Parosmia can also alter your sense of taste.

Some people also experience phantosmia in addition to parosmia.

Symptoms of parosmia may occur after recovering from an injury or illness such as infection, neurological conditions, or chemical exposure.

In some cases, symptoms can be temporary, whereas in others, they may become chronic.

Possible causes of parosmia

Your ability to detect and perceive smells depends on the health of your olfactory bulb. 

The olfactory bulb is a small structure located behind the nasal cavity. It contains neurons that send signals to the brain to enable you to interpret smells.

If the olfactory bulb is damaged, it may affect the way smells are processed, leading to symptoms of parosmia.

In some cases, clinicians are not sure what causes parosmia. There may not be one identifiable cause or event that led to the onset of symptoms.

Bacterial or viral Infection 

Upper respiratory infections are a common cause of parosmia. This can include the common cold and other infections, such as COVID-19.

Infections can cause damage to the olfactory neurons and disrupt communication between the olfactory bulb and the brain.

However, not everyone who has an infection will develop parosmia.

Chemical exposure and smoking

Long-term or high exposure to certain chemicals can also lead to symptoms of parosmia and other olfactory changes.

Chemicals that can cause parosmia include:

  • anesthetics
  • cleaning chemicals
  • gasoline
  • metal compounds
  • tobacco

Radiation and chemotherapy

Some cases of parosmia occur as a side effect of radiation and chemotherapy.

Doctors commonly use radiation and chemotherapy treatments to target and kill cancer cells. They may also use them to address other conditions. However, these treatments can change the way the olfactory neurons behave.

Other possible side effects of radiation and chemotherapy include nausea and fatigue.

Head injury

Head injuries can cause many types of olfactory disorders, including parosmia. In fact, head injuries account for about 5–17% of all cases of smell and taste disorders.

The degree of an olfactory disorder caused by a head injury depends on several factors. These include the severity of the injury, the location of the injury, and age.

Common causes of head injuries include contact sports and vehicular accidents.

Neurological conditions

Neurological or nerve conditions can also cause parosmia. This is because they can change the way smells reach the brain.

Neurological conditions that can lead to parosmia include:

One 2020 study suggests that olfactory dysfunctions occur in 45–90% of people with Parkinson’s disease. Additional research suggests that about 27.2% of people with MS will experience olfactory dysfunction.

Tumors and cancer

Brain and neck tumors can put pressure on areas of the brain responsible for processing smell. In some cases, this can lead to parosmia. However, people who have tumors may instead experience phantosmia or other olfactory symptoms.

Nasal or paranasal sinus cancers can also affect your sense of smell if they affect the olfactory bulb.

Other sinonasal conditions

Other conditions that affect your nose or sinuses may lead to parosmia. They may also cause other olfactory symptoms such as a loss of smell (anosmia).

Other conditions that may lead to parosmia include:

Parosmia and COVID-19

Parosmia can sometimes occur as a short or long-term complication of COVID-19.

Researchers from a 2021 study found that infection from SARS-CoV-2, the virus that causes COVID-19, can cause damage to the olfactory neurons. This can disrupt how smells are processed.

Anosmia and a loss of taste (ageusia) are other symptoms commonly associated with COVID-19. One study that observed 27,492 people with COVID-19 showed that 47.85% had symptoms of olfactory dysfunction.

In some cases, these symptoms go away on their own over time. In others, symptoms may be more chronic and might benefit from treatment.

If you have symptoms of COVID-19 or new changes to smell or taste, self-isolate and contact your doctor about treatment.

When to seek medical help

Contact your doctor if you have any new or persistent olfactory symptoms. These can include phantosmia and other symptoms such as a loss of smell or altered sense of taste.

Your doctor can help you develop a treatment plan to address your symptoms and diagnose the underlying cause.

Diagnosis for parosmia

To diagnose parosmia, your doctor may ask questions about your lifestyle and medical history.

This may include questions about any recent illnesses, exposure to chemicals, or your smoking habits.

Your doctor may also assess the function of your olfactory bulb. They may provide substances for you to smell and ask you to describe their scent.

If your doctor believes a physical condition could be causing your symptoms, they may conduct a physical exam or laboratory tests. These will help them determine the underlying cause.

Tests for determining underlying physical conditions may include:

Treatment for parosmia

Some cases of parosmia go away on their own over time. This can happen if the neurons recover and the full ability to smell returns.

Other cases of parosmia may require treatment.

Treatment for parosmia focuses on resolving the underlying cause. For example, if a bacterial infection is causing your parosmia, your doctor may recommend antibiotics.

If your parosmia is the result of a medication or clinical treatment, your doctor may help you adjust your treatment. They will then check to see if your symptoms resolve.

However, it is important to continue with treatments or medication your doctor has prescribed unless they advise you otherwise.

Treatments for parosmia can include:

  • Food supplements: Zinc and vitamin supplements may help improve olfactory processing.
  • Smell training: This involves exposing yourself to different scents in order to retrain your sense of smell. 
  • Surgery: This involves surgically removing any nasal obstructions, such as polyps or tumors.

At-home treatment for parosmia

You may be able to treat parosmia at home. At-home treatments include smell training recommended by your doctor that you can perform yourself.

If an environmental factor such as chemical exposure or smoking is the cause of your symptoms, it may help to avoid them. Ongoing exposure can lead to complications.

Complications of parosmia

Without treatment, parosmia can lead to more serious health issues.

These can include:

If the symptoms of your parosmia are unpleasant, it can also impact your quality of life.

You can avoid complications from parosmia by seeking treatment early. Treatment interventions may also help alleviate complications once they have developed. 

Impairments to your sense of smell can also be dangerous. Your sense of smell can help you identify risks such as food that has expired, smoke, or chemical or gas leaks. Make sure your home is fitted with working carbon monoxide, gas, and smoke detectors if you experience parosmia or other changes to smell.

Outlook and recovery

If your parosmia is not improving, you should seek medical treatment.

In some cases, changes to your sense of smell are not treatable and can be permanent. However, treating the underlying cause can be important for your health and improve your quality of life. Your doctor might also recommend methods to manage chronic symptoms even if they cannot be completely resolved.

In other cases, treatment may resolve your symptoms and can even speed up the recovery time.

Frequently Asked Questions

Below are some frequently asked questions about parosmia.

How long does parosmia last? 

Parosmia can last for days, months, or even be permanent.

The duration and severity of symptoms can vary widely depending on the cause, extent of any damage to the olfactory system, and other factors.

Does parosmia go away?

Many cases of parosmia go away on their own or with treatment‌.

Some cases of the condition, however, may become chronic or permanent.

Is parosmia dangerous?

Parosmia is not always serious and can be resolved.

However, sometimes parosmia can lead to complications such as food aversion, weight loss, depression, and other health effects.

Changes to the way you perceive smells can also be dangerous. Smell is a useful sense for detecting risks such as chemical exposure, gas leaks, and expired food.

Summary

Parosmia refers to a distorted sense of smell. It can have a variety of causes, including head injury, chemical exposure, and some nasal conditions. Parosmia can also occur as a complication of COVID-19 and other infections.

Parosmia occurs when the olfactory neurons or brain is damaged, disrupting how smell information is processed.

Treatments for parosmia focus on healing the olfactory bulb, a neural structure in the nasal cavity that helps you process smells.

Contact your doctor if you have new symptoms of parosmia or changes to smell or taste.

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Medical Reviewer: Darragh O'Carroll, MD
Last Review Date: 2022 Jun 28
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