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Understanding Loss of Smell

Has a smell ever taken you back to a childhood memory or made you feel a strong emotion? That’s because the smell-processing center of the brain, the olfactory bulb, sits right next to the amygdala, the emotional processing center, and the hippocampus, the place where memories are stored.

“Our sense of smell has a lot to do with how we perceive the world,” says Northwestern Medicine Otolaryngologist Sameer A. Alvi, MD. “A loss or decline in sense of smell is very common — many studies suggest it’s more prevalent than hearing loss — and can be life-changing.”

Anosmia is complete loss of the ability to smell. Hyposmia, more common than anosmia, is a decrease in the sense of smell. And because smell and taste are closely linked, decline in smell also often means decline in taste.

Causes of Smell Loss

Age

“After the age of 65, 60% of people have major olfactory impairment, and nearly 25% of people are completely anosmic,” says Dr. Alvi.

Inflammation

Allergies, chronic sinusitis and nasal polyps all cause inflammation in the nasal passages, which can decrease the ability to smell.

“There are certainly some reversible causes of olfactory impairment due to inflammation. Other times, after a bad cold or the flu, people can also develop permanent smell impairment,” says Dr. Alvi. “The mechanism of this injury is not completely understood right now.”

This type of smell loss can last for a while — weeks, months and sometimes even years.

Trauma

Head injuries, including concussions or fractures of the skull, can sometimes damage the nerves that connect the nose to the brain, leading to hyposmia or anosmia. Loss of smell has been shown to occur in up to 17% of people following head trauma incidents.

Neurologic Disorders

Smell impairment is also often a symptom of Parkinson’s disease and Alzheimer’s disease.

Tumors

“Although rare, smell loss can sometimes result from tumors in the nasal cavity or the brain,” says Dr. Alvi.

Cancer Treatment

Chemotherapy and radiation therapy may cause smell impairment. “Especially if your radiation therapy involves the base of the brain or the nasal passages,” adds Dr. Alvi.

Treatment for Loss of Smell

Is smell loss reversible? That depends on the underlying cause.

Smell loss caused by inflammatory disease like allergies, or chronic sinusitis associated with nasal polyps can be significantly improved by treating the inflammatory disease itself.

“For these patients, using steroids to manage their inflammatory process can often lead to improvement in smell,” says Dr. Alvi.

For all other causes of loss of smell, and the instances where the cause is unknown, there is less of a chance of recovering the sense. However, there is some hope for improvement with emerging smell therapies.

When to Talk to Your Physician

“Anybody who feels they have significant smell impairment should be evaluated by an ear, nose and throat (ENT) physician,” says Dr. Alvi. “The sooner you can be seen, the better.”

Your physician will go through your personal history and complete a physical examination, typically involving a nasal endoscopy, to determine if further testing is required.

Sameer A. Alvi, MD
Sameer A. Alvi, MD
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