Parosmia - Causes, Diagnosis, and Treatment

Creator: Dr. P. Reshma Gladys
Published: 2022-10-26T16:50:58

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Parosmia refers to a medical condition in which the sense of smell is altered, and it is difficult to understand the intensity of the smell.

Written by

Dr. P. Reshma Gladys

Medically reviewed by

Dr. Syed Peerzada Tehmid Ul Haque

October 26, 2022

June 19, 2023

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Contents

What Is Parosmia?
What Causes Parosmia?
How Is Parosmia Diagnosed?
What Are the Treatments for Parosmia?
What Are the Complications of Parosmia?
Can One Recover From Parosmia?

What Is Parosmia?

Parosmia is a qualitative olfactory disorder characterized by an abnormal perception of olfactory stimulus (smell). Sometimes the person with parosmia will find that the smell which is pleasant seems unpleasant for him or her, or the smell that he or she used to like now seems unpleasant. It could be due to parosmia. If a person has parosmia, then either the sense of smell seems to be altered or distorted, or completely lost. This parosmia can be temporary or permanent and will depend on the cause.

What Causes Parosmia?

Parosmia can occur when the neurons that detect the scent are damaged or are affected by any medical condition. These neurons are present in the lining of the nose and send signals to the brain, and the brain interprets the smell. The neurons may be damaged or affected due to viral infections or other medical conditions. When these neurons are damaged, it changes the way the brain interprets any smell.

These signals from these neurons are received in the olfactory bulbs present underneath in the front of the brain, and they interpret whether the smell is pleasing, enticing, appetizing, or foul. Any damage to these olfactory bulbs can also be the reason for parosmia.

The conditions that can cause parosmia are briefly discussed below:

Bacterial or Viral Infection - One reason for parosmia is the damage to the olfactory neurons from a cold or a viral infection. Upper respiratory infections can cause damage to these olfactory neurons. These occur mostly in older patients as compared to younger patients with the same infection.
Head Injury or Brain Trauma - Injury to the brain from trauma is linked to parosmia due to olfactory damage. The duration and severity of the parosmia depend on the injury. Parosmia from injury can also be due to damage to the olfactory nerve fibers at the cribriform plate (part of the skull). This can also be caused by seizures which will affect the brain.

Chemical and Smoking - Parosmia can also be caused due to damage to the olfactory neuron from smoking. This can happen gradually. Likewise, exposure to chemical toxins can also cause damage and eventually result in parosmia.
Side Effects from Cancer Treatment - Radiation and chemotherapy, which are done as a part of cancer treatment, have been reported to cause parosmia in many patients.
Neurologic Conditions - Conditions like Alzheimer’s and Parkinson's disease have been seen to affect the olfactory senses. One of the early arising symptoms of Alzheimer’s disease and Parkinson’s disease is parosmia. Other conditions like Lewy body dementia and Huntington’s disease can also cause this.
Tumors - One of the rarest causes of parosmia is a tumor on the olfactory bulbs in the frontal cortex.
Covid-19 Infection - Covid-19 infection is seen widely to cause anosmia (that is, loss of smell) in affected patients and is seen to revert back once the infection subsides. In some patients, it is seen to cause parosmia by affecting the olfactory system.

How Is Parosmia Diagnosed?

For parosmia, you may have to consult an otolaryngologist, also known as ENT (ear, nose, and throat) specialist.

During the visit, certain things will be presented, and the patient has to describe the scent and rank them according to their quality.
One of the common tests to diagnose parosmia involves a small booklet of “scratch and sniff” items that the patient needs to test and respond to the doctor.
The doctor will ask for the family history of cancer and any neurologic conditions, history of any recent infections, lifestyle factors, and medicines that are taken.

If the doctor suspects that the cause could be due to cancer or any neurologic problem, they may suggest other investigations, which include:

CT scan.
Biopsy of the sinus.
MRI scan.

What Are the Treatments for Parosmia?

The treatment for parosmia depends upon the severity and the cause of the parosmia. In most cases, the senses return back to normal once the causative factor is stopped or removed. In some cases, like in the case of tumors and nasal obstruction like nasal polyp is the reason for the parosmia, then surgery might be required to remove the causative factor.

Treatment for parosmia includes:

Zinc.
Vitamin A.
Antibiotics in case of infections.
Topical steroids and antihistamines have significantly improved parosmia cases associated with allergic and post-infective rhinosinusitis.
Olfactory training.

There is no treatment for parosmia, which occurs as a result of viral infections like Covid-19 or head injury. The injured or damaged nerve fibers can grow back in your nose and nasal cavity, and the sense of smell will be fully or partially recovered.

What Are the Complications of Parosmia?

For healthy living, all the organs and senses should be functional in our bodies. If we have any health-related issue, it greatly affects the quality of our life. Smell plays an important part in life; like for enjoying food, the sense of smell plays a major role. It also plays an important role in professions like chefs, perfumers, and firefighters. In such people, parosmia may make it hard for them to do their job. Also, parosmia can have other effects and can lead to problems like:

Loss of appetite.
Weight loss.
Depression.

Can One Recover From Parosmia?

Parosmia is not a permanent condition in most cases. If the parosmia is caused due to any damage to the nerve fibers, this can be recovered once the nerve fibers grow back. In the majority of cases, parosmia is caused due to viral infections, which are reverted back once the infection subsides. But in some patients, it may take a long time for the sense to recover to normal.

The recovery rate depends on the cause of the condition and also the treatment for the same. Also, it will depend upon the patient's factors, like age and pre-existing medical conditions.

Conclusion

Parosmia is a condition that affects the sense of smell. It could be caused by infection, brain trauma, smoking, chemical fumes, or medications. The recovery depends upon what causes parosmia. The condition is recovered once the triggering factor is removed. This condition greatly affects the quality of life. Consult a doctor when you start to experience any change in the way you sense smell. The prognosis is always good for this condition.

Frequently Asked Questions

1. How Does a Substance Smell to Those With Parosmia?

Individuals with parosmia may be unable to appreciate their environment's full range of smells. The scents smell ‘distorted’ to them. For example, warm, freshly baked cookies may smell sweet and delicious to many people but unpleasant and rotten to those with parosmia. Likewise, the sweet scent of a flower may smell like rotten meat. Factors like head injury, sinus infections, and so on can trigger parosmia.

2. Who Is Prone to Get Parosmia After COVID-19?

If one experiences loss of taste and smell as the primary symptom of COVID-19 infection, then such individuals are more prone to developing parosmia. Age and sex may also contribute to developing parosmia after COVID-19. A study involving 268 people affected by parosmia after COVID-19 infection showed that about 70.1 % were 30 years old or younger, and about 73.5 % were females. The parosmia experienced by these people ranged from merely altered to profoundly disgusting.

3. What Should Those With Parosmia Eat?

A physician may prescribe medications to overcome parosmia. However, one can consume steamed or poached meats, steamed vegetables, plain yogurt, unflavored protein shakes, plain rice, plain bread without the crusts, plain pasta, cheese, and plain dairy products. Foods at room temperature or cold foods can be eaten. Fried foods, onions, garlic, eggs, roasted meats, chocolates, and coffee should be avoided.

4. Can Parosmia Be Treated?

Not all cases of parosmia can be treated. If parosmia is a consequence of environmental factors, cancer treatment, smoking, or medication, the sense of smell can be restored once the triggering factors are eliminated. If parosmia is due to nasal polyps or tumors, surgery may be required to remove the polyps and tumors, eventually restoring the sense of smell. In about 60 % of cases with parosmia due to infection, the sense of smell was restored once the infection was eliminated from the body.

5. Can Phantosmia Be Treated?

Smelling things that are not present in one’s environment is called phantosmia. It can cause an unpleasant feeling and can impact how things taste. Phantosmia due to head injury or a viral infection like COVID-19 cannot be treated. In most cases, phantosmia is a temporary condition that gets corrected within a few weeks. Damaged nerves in the nose and nasal cavity do have the potential to grow back. Hence, the sense of smell can be restored partially or completely without treatment.

6. Why Does Someone Suddenly Feel Like They Smell Bad?

Olfactory Reference Syndrome (ORS) or olfactory reference disorder is a serious and underrecognized condition that is similar to Body Dysmorphic Disorder (BDD) and Obsessive-Compulsive Disorder (OCD). Individuals with this disorder feel that they smell bad, but actually, they do not. Another rare condition is trimethylaminuria, in which the metabolic processes in the body fail to alter the trimethylamine chemical. Trimethylamine is known for its unpleasant smell.

7. Is Parosmia Part of Long-Term COVID-19 Infection?

The most common symptom of COVID-19 infection is the loss of taste and smell. However, one regains the lost sensations during the recovery period. However, a few people may continue to experience an alteration in their olfactory (related to smell) sensations for about three to four months following the infection. The average duration of parosmia in COVID-19 patients was found to be about 3.4 months.

8. Is It Rare to Develop Parosmia Following a COVID-19 Infection?

There is a variation in the number of people affected by parosmia and loss of taste following COVID-19 infection. It was found that parosmia and loss of taste following COVID-19 infection affected about 50-75 percent of the people. About 25 - 75 percent of individuals continue to develop parosmia in the recovery period. The average onset of parosmia in individuals with COVID-19 is three months following the initial infection.

9. Is Parosmia Linked to Stress?

Research has found that smell and taste stimuli could be affected by stress. However, stress is more linked to phantosmia than parosmia. A few individuals who feel stressed can experience false or phantom smells. This is called phantosmia or olfactory hallucinations. Those with anxiety can sometimes smell odd smells that other people cannot feel. The phantom smells could be odd, strong, metallic, sour, blood-like, acidic, ammonia-like, pungent, etc.

10. What Is the Innovation in the Treatment of Parosmia?

Recently, injections of platelet-rich plasma obtained from the individual’s blood have been used to treat parosmia. But, further studies are required for the same. Another treatment is olfactory retraining therapy. Individuals with parosmia are asked to smell strong-smelling scents like cloves, eucalyptus, or citrus substances to reform normal responses to the nose and brain.

11. Which Part of the Brain Is Responsible for Causing Phantosmia?

Smelling things that are not present in one’s environment is called phantosmia. It can cause an unpleasant feeling and can impact how things taste. Damages in the brain's frontal lobe can cause phantosmia since this part of the brain is responsible for the conscious perception of various odors. Phantosmia can be due to an upper respiratory infection or a head injury. Other causes include aging, temporal lobe seizures, inflamed sinuses, Parkinson’s disease, certain medications, etc.

12. Can Smoking Cause Parosmia?

Individuals with parosmia may be unable to appreciate their environment's full range of smells. The scents smell ‘distorted’ to them. The chemicals and toxins in cigarettes can result in parosmia over time. Similarly, high levels of air pollution and exposure to toxic chemicals can also result in parosmia. Parosmia due to environmental factors like smoking, certain medications, or chemical exposure can be corrected once the underlying triggering factor is eliminated.

13. Does Chemotherapy Result in Parosmia?

Parosmia can develop as a severe and potentially life-threatening consequence of chemotherapy. The smell receptors and taste buds comprise a few renewable cell tissues. However, these tissues' cell renewal is inhibited during chemotherapy and radiation therapy, which causes parosmia. As a result of chemotherapy, some may be unable to smell certain things or can become highly sensitive to specific smells.

14. Can One Recover From Parosmia Quickly?

In a few cases, parosmia can be permanent, but most recover completely within a few weeks but it may also take some months to resolve in a few cases. If parosmia is a consequence of environmental factors, cancer treatment, smoking, or medication, the sense of smell can be restored once the triggering factors are eliminated. In about 60 % of cases with parosmia due to infection, the sense of smell was restored once the infection was eliminated from the body.

15. Does Parosmia Worsen With Time?

The good news is that parosmia resolves with time in most cases. Individuals have reported that they have regained their sense of smell within three to four months following an infection. About 80 to 90 percent of people regain their senses within two years. In a few cases, parosmia can be permanent, but usually, most recover completely within a few weeks.

16. What Is Neuroendocrine Cell Hyperplasia of the Lungs?

Neuroendocrine cell hyperplasia of the lungs is a disease in which the number of neuroendocrine cells in the lung tissue is higher than normal. It is common in babies with pulmonary hypertension, a disease that makes it hard for blood to flow through the lungs.

17. Does Neuroendocrine Cell Hyperplasia of Infancy Pulmonary Hypertension Involve?

Cancer of the neuroendocrine cells in the stomach is called neuroendocrine carcinoma gastric. It is a rare type of cancer that can have different effects, from slow-growing tumors to ones that spread quickly.

Sources

Dr. Syed Peerzada Tehmid Ul Haque

Otolaryngology (E.N.T)

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