What Is Parosmia?

Parosmia is a change in your perception of smell. If you have parosmia, a scent with which you were once familiar might smell different. Or, scents that were once pleasing to you may no longer be; instead, the scents can be off-putting to you.

Sometimes, the distortion to smell can be so extreme that you experience nausea and vomiting.

Coffee, meat, and onions are some examples of food smells that have been most commonly reported as being distorted among people with parosmia. Coffee has been described as smelling "burnt," while the smell of meat and onions have been described as "rotten."

Scents typically regarded as foul, like that of feces, may also no longer be to you—you might find the smell positive or be unable to detect it.

In addition to a distorted smell perception, you may also notice with parosmia that food tastes bland and that your eating habits have changed because of that.

What Causes Parosmia?

Your sense of smell is a function of the nerve tissues located in the nose. As you breathe, scent molecules make their way past the scent receptors in the nose, prompting a signal to the brain and registering as a familiar or unfamiliar smell.

Parosmia develops when the nerves that detect scents become damaged after some experience that impacts the olfactory (smelling) sense. There's not always an obvious cause of parosmia, but some of the most common include:

• Viral or bacterial infection
• Smoking
• Head injury 
• Exposure to a chemical, like ammonia, solvents, or nickel
• Certain medications, including antihistamines, antibiotics, and selective serotonin reuptake inhibitors (SSRIs)
• Chemotherapy and radiation treatments
• Neurological conditions, like Alzheimer’s and Parkinson’s diseases
• Growths in the nasal cavity

COVID-19 is an example of a viral infection that can cause parosmia. In the case of COVID-19, parosmia might develop on its own or after a complete loss of smell. While parosmia is unsettling, it can be a positive sign in recovery since it indicates that you're regaining your sense of smell if you are someone who had completely lost it at first.

How Long Does Parosmia Last?

It’s difficult to predict exactly how long a case of parosmia will last. How long you experience the distortion depends on how quickly your olfactory nerves can repair themselves from the damage—this timeline seems to vary widely by person and cause of the parosmia.

Most instances of parosmia aren't permanent, but it may take anywhere from months to years for your sense of smell to get back to normal. For instance, it seems like parosmia from COVID-19 can take 14-16 months.

How Is Parosmia Diagnosed?

An otolaryngologist—a doctor who specializes in the ear, nose, and throat—is usually the person to diagnose parosmia. An otolaryngologist might also be called an ENT.

An ENT will start assessing your smelling ability by examining your ears, nose, and throat and reviewing your health history. As part of reviewing your history, they might ask whether you've been exposed to any toxic chemicals or have been injured to try to figure out a cause.

The ENT will then administer a smell test. For example, the doctor might give you a special scratch-and-sniff book and have you identify the different scents on the pages. Incorrectly identifying the smell might indicate parosmia.

How Can You Treat Parosmia?

Sometimes your sense of smell can go back to normal spontaneously. Other times you may need treatment. There are some treatment options available that may help get your scent perception back to normal.

Depending on the underlying cause of the parosmia, your healthcare provider might recommend:

• Removing an environmental trigger, like stopping smoking or avoiding exposure to a particular chemical
• Having surgery to repair an obstruction, like a polyp (growth) or tumor in the nose that's impacting the function of your olfactory nerves
• Taking medications to help with an infection or other health condition, such as taking corticosteroids, antibiotics, or a nerve medication like gabapentin (which is sold under brand names like Gralise, Horizant, and Neurontin)
• Changing your medication or your medication dosage, if it's determined that your medication is causing your scent distortion
• Engaging in olfactory training therapy, which involves sniffing different types of odors daily over a period of time to eventually restore olfactory nerve function.

There are a few other alternative therapies that have been anecdotally helpful for some people. For example, some studies have reported that vitamin A and zinc could help revive your scent perception. Other studies have noted that acupuncture and a nerve-stimulating procedure known as transcranial magnetic stimulation might be beneficial. More research and scientific evidence is needed to confirm these theories, though.

A Quick Review

Parosmia is a change in your sense of smell. Many people experience parosmia as perceiving a previously pleasant scent as suddenly foul or unbearable. It typically develops after you've had an infection, head trauma, chemical exposure, or other health condition. The length of a parosmia episode can widely vary based on the cause, lasting weeks to years. Depending on the underlying cause, treatment can include smell training, medications to clear an infection, surgery to remove an obstruction, or avoiding the trigger.