What is the Difference Between Parosmia and Anosmia

The key difference between parosmia and anosmia is that parosmia is the change in the normal perception of odours while anosmia is the complete inability to detect odours.

People who normally undergo smell disorders experience either complete loss of smell or changes in the way they perceive odours. Smell disorders have many causes, including upper respiratory tract infection, injury to the head, polyps in the nasal cavities, sinus infections, hormones disturbances, dental problems, exposure to certain chemicals like insecticides and solvents, some medicines, and radiation. There are different kinds of smell disorders, and parosmia and anosmia are two types of them.

CONTENTS

1. Overview and Key Difference
2. What is Parosmia 
3. What is Anosmia
4. Similarities – Parosmia and Anosmia
5. Parosmia vs Anosmia in Tabular Form
6. Summary – Parosmia vs Anosmia

What is Parosmia?

Parosmia is the change in the normal perception of odours. In parosmia, something that normally smells pleasant can later smell foul. Sometimes, in this health condition, the smell of something familiar is distorted. If people suffer from parosmia, they may experience a loss of scent intensity – meaning that they can’t detect the full range of scents around them. Moreover, in parosmia, people who suffer can detect an odour that is present around them, but the scent smells wrong to them. For example, the pleasant and subtle odour of freshly baked bread might smell overpowering and rotten.

The main symptoms of parosmia include sensing a persistent foul odour, especially when food is around, difficulty to recognize some scents in the environment, and scents one used to find pleasant may later become overpowering and unbearable. The causes of parosmia include upper respiratory infections such as cold, head injury, sinus infection, certain toxins and drugs, seizures in the temporal lobe, brain tumors, COVID-19, and constant dry mouth. A common test for detecting this condition involves a small booklet of “scratch and sniff” beads that people respond to under the doctor’s observation. The diagnosis methods include family history check, sinus CTs, biopsy of the sinus region, and MRI. Furthermore, the treatments for parosmia include zinc, vitamin A, antibiotics, and surgery to correct nasal obstructions.

What is Anosmia?

Anosmia is the complete inability to detect odours. It is also called smell blindness. This health condition can be temporary or permanent. It also differs from hyposmia, which is a heath condition that has decreased sensitivity to some or all smells. The causes for anosmia include nasal congestion from a cold, allergy, and sinus infection, nasal polyps, injury to nose and smell nerves, exposure to toxic chemicals such as pesticides or solvents, certain medications (antibiotics, antidepressants, anti-inflammatory medication, heart medication), cocaine abuse, old age, certain medical conditions (Alzheimer’s disease, Parkinson disease, multiple sclerosis, nutritional diseases, congenital diseases, hormonal disturbances) and radiation.

Figure 01: Anosmia

The symptoms of anosmia may include loss of sense of smell gradually or suddenly and smell familiar scents differently before developing a complete loss of smell. Furthermore, this condition can be diagnosed through family history, psychophysical assessment, nervous system examination, and smell testing kits. Furthermore, anosmia can be treated through glucocorticoids (prednisone), steroidal treatment for nasal polyps, surgery to remove nasal polyps, and gene therapy.

What are the Similarities Between Parosmia and Anosmia?

• Parosmia and anosmia are two types of smell disorders.
• In these conditions, people may experience changes in the way they perceive odours or experience either complete loss of smell.
• Both health conditions can be caused due to similar reasons, such as infections and nasal obstructions.
• They are treatable with medications and surgeries.

What is the Difference Between Parosmia and Anosmia?

Parosmia is the change in the normal perception of odours, such as something that normally smells pleasant later smells foul, while anosmia is the complete inability to detect odours. Thus, this is the key difference between parosmia and anosmia. Furthermore, parosmia is caused by upper respiratory infections such as cold, head injury, sinus infection, certain toxins and drugs, seizures in the temporal lobe, brain tumors, COVID-19, and constant dry mouth. On the other hand, anosmia is caused by nasal congestion from a cold, allergy and sinus infection, nasal polyps, injury to nose and smell nerves, exposure to toxic chemicals such as pesticides or solvents, certain medications (antibiotics, antidepressants, anti-inflammatory medication, heart medication), cocaine abuse, old age, certain medical conditions (Alzheimer’s disease, Parkinson disease, multiple sclerosis, nutritional diseases, congenital diseases, hormonal disturbances) and radiation.

The below infographic presents the differences between parosmia and anosmia in tabular form for side by side comparison.

Summary – Parosmia vs Anosmia

Parosmia and anosmia are two types of smell disorders that are due to loss of olfactory senses. Parosmia refers to the change in the normal perception of odours, while anosmia is the complete inability to detect odours. So, this is the key difference between parosmia and anosmia.

Reference:

1. Watson, Kathryn. “Parosmia.” Healthline, Healthline Media.
2. Marks, Hedy. “Anosmia: Symptoms, Causes, and Treatments.” WebMD.

Image Courtesy:

1. “Anosmia.” By Manu5 – Scientific Animation (CC BY-SA 4.0) via Commons Wikimedia

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