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We spend our days interacting with the world around us through our senses of sight, sound and touch.

But anyone who has developed complete nasal obstruction from an infection or severe allergies has experienced what it’s like to be without one of our most basic senses: our sense of smell.

In other animals, the sense of smell is crucial for survival, reproduction and rearing of young. Although humans can survive without smell, research has shown that losing the sense of smell negatively impacts quality of life, even driving some people toward clinical depression.

Just as other animals depend on their sense of smell as an alarm system for danger, we also depend on smell to warn us of such hazards as smoke from a fire, natural gas leaks in the home or spoiled food. Also, the flavor of a meal depends heavily on our ability to smell.

Scents round out our experiences and are often integral parts of our memory of events. Memories of a perfume worn by your spouse or the bread being baked at your grandmother’s house when you were a child last for decades, and are often intricately tied in with strong emotions.

Problem is fairly common

Smell disorders affect 19% of the population over the age of 20 and 25% of the population over 53. If smell loss from aging alone is considered, one out of eight people between 53 and 91 will be affected over a five-year period.

The detrimental effect of smell loss on flavor of food could significantly impact older adults, for whom diet and nutrition may already be a concern.

The sense of smell (olfaction) is dependent on millions of specialized nerve cells that are located in a deep protected recess high in the nasal cavity.

Remarkably, these nerve cells normally die and are replaced throughout our lifetime. Therefore, the system has the capacity to repair itself after injury. But this isn’t always possible or complete.

The most common causes of prolonged smell loss occur as a result of upper respiratory infection, head injury, chronic sinus disease and aging. However, other conditions such as Alzheimer’s disease, Parkinson’s disease and tumors can also be associated with smell loss.

In some cases, the loss of smell is complete (anosmia), while in other cases there is only a partial loss (hyposmia).

In many instances where smell loss occurs, remaining smells are distorted. Most patients report that these distorted odors are unpleasant: “smoky,” “swamp-like,” “musty,” “garbage” or “chemical-like.”

Treating the condition

In cases where smell loss results from sinus disease, doctors have had some success in treating the condition. Oral and topical steroids often provide relief. Sometimes surgery is required to reduce the obstruction of odors to the sensory nerve cells.

Sinus disease usually requires long-term management, and fluctuations in the ability to smell are common.

Unfortunately, people with loss of smell resulting from head injury, upper respiratory infection or aging don’t often improve.

The natural ability of the olfactory system to repair itself allows for some patients to regain the sense of smell after a respiratory infection-related loss or head injury. This recovery can take over a year, and can be so gradual that people have difficulty recognizing the change.

If you experience any persistent change in your sense of smell, visit your doctor. Some rare forms of smell disorders may result from tumors in the brain, neurodegenerative disease or infection.

In addition, your doctor should talk to you about risks, such as depression and nutritional concerns that may stem from loss of smell.

Ongoing scientific work is investigating how stem cells in the nose replace dying olfactory nerve cells. In the future, we will be able to trigger these cells to make more neurons, or replace missing stem cells to regenerate the neurons.

Or we may be able to electrically stimulate a sensation of smell using an artificial implant.

Eric Holbrook, M.D., is a contributor to Harvard Health Publications.

© 2019 President and Fellows of Harvard College. All rights reserved. Distributed by Tribune Content Agency, LLC.