What Causes Loss of Smell?

In This Article

The Centers for Disease Control and Prevention says loss of smell—or anosmia—may be a sign of COVID-19 infection. If you suspect you or a loved one may be sick, contact your doctor. Learn more about COVID-19, including how it's diagnosed and answers to common questions you may have.

People often take for granted the ability to smell, but people with a diminished sense of smell or who have lost this sense completely know that this ability is linked to their overall quality of life. It is a major contributor to the ability to taste food, and people who lose their sense of smell often lose their appetite. 

If you are losing your sense of smell, you may have noticed that things taste differently. In fact, the two senses are so connected that people who are losing their sense of smell often mistakenly believe they are losing their sense of taste.

Your sense of smell can also warn you when you might be in danger. For example, the smell of smoke alerts you of fire, and noxious chemical smells force you to leave an area before these chemicals can damage your lungs or other parts of your body.

Many people associate certain smells with pleasant memories or find certain smells comforting. For example, if your grandmother's house smelled like cinnamon rolls, you may find this smell comforts you when you're stressed out or not feeling well.

Woman smelling leaves while sitting at table in perfume workshop
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Overview

The loss of one's ability to smell is called anosmia. Many conditions can temporarily or permanently cause anosmia. More rarely, a decreased sense of smell can signal the start of a serious condition such as Alzheimer's disease or Parkinson's disease. Some people are born with a diminished or heightened ability to smell as compared to others.

In general, our ability to smell may wax and wane over our lifetime, and most of us begin to lose our sense of smell after the age of 60. Studies also show that women tend to have a more accurate sense of smell than men.

In addition to a diminished sense of smell and taste, people who suffer from anosmia may also have other symptoms depending on the cause of their anosmia. These symptoms vary widely. You should report any unusual symptoms to your doctor, even if you don't think they're relevant, since they may indicate an underlying condition.

Causes

If you're concerned that you might be losing your sense of smell, it's likely you have a common and temporary condition. Keep in mind that each individual and case is different, so whether or not your diminished sense of smell persists will depend on your individual circumstances.

The following conditions can cause anosmia that is often temporary or reversible:

  • Allergies
  • Congestion from colds or upper respiratory infections
  • Dental problems or oral surgery
  • Deviated septum
  • Nasal polyps (often must be treated surgically)
  • Sinusitis
  • Temporary fluctuations in hormone levels
  • Vitamin deficiencies or malnutrition (rare)

The loss of smell due to some conditions or risk factors may be reversible, partially reversible, or permanent. For example, once a person quits smoking, their sense of smell usually improves—but how much the ability to smell returns is variable.

Medication side effects that cause loss of smell may be temporary or permanent, depending on the medication.

Zinc nasal sprays are known to cause permanent anosmia. Breathing in chemicals or environmental pollutants has been known to cause permanent anosmia as well.

The use of cocaine or other drugs that are snorted up the nose can cause anosmia. Like smoking, a person's ability to smell may or may not return when the drug is stopped or may only partially return.

The list of medications that may alter a person's ability to smell or taste is very long, but it includes many antibiotics, antidepressants, blood pressure, and heart medications.

Associated Conditions

Many conditions often cause a permanent loss of a person's sense of smell. Again, keep in mind that each case is different, and some people may regain their sense of smell even with these conditions, though many do not.

It's common for a person to lose the sense of smell due to the normal aging process. Brain injuries (head trauma) may cause anosmia, as can disorders that affect the nervous system, including Parkinson's disease, multiple sclerosis, or Alzheimer's disease. Radiation treatment to the head and neck may also cause anosmia.

Conditions that may cause anosmia in rare cases include:

Consider using an online symptom checker if you think you are losing your sense of smell or have one of the conditions above.

Diagnosis

Your doctor will review your medical history as well as any current symptoms you might be having. Your doctor will probably also perform a physical exam.

If warranted, the physician will order blood tests to rule out risk factors, such as infections or hormonal disturbances, or a computerized tomography (CT) scan or magnetic resonance imaging (MRI) to diagnose nasal polyps or tumors.

Doctors may also administer a scratch-and-sniff test (in which you will be asked to identify certain smells) or a taste test.

When You Should See a Doctor

Any unexplained loss of smell that lasts longer than a cold virus probably should be checked out by a doctor. Call your doctor immediately if your inability to smell comes on suddenly and is accompanied by other worrisome or strange symptoms.

Go to the emergency room if you lose your sense of smell and experience neurological symptoms such as dizziness, slurred speech, or muscle weakness.

Treatment

As mentioned above, many conditions that can diminish your sense of smell are reversible, but it depends on the root cause of your condition. Nasal polyps or deviated septums can be treated surgically, sinusitis can sometimes be treated with antibiotics, and allergies can be treated with medications.

If the anosmia is a side effect of a medication you are taking, the medication should be stopped. There is no medication or treatment specifically designed to improve or bring back your sense of smell, but finding the cause of the anosmia and resolving the underlying issue is successful in many cases. In some cases, the sense of smell may return gradually.

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Additional Reading
  • American Academy of Otolaryngology - Head and Neck Surgery. Smell and Taste. 
  • American Family Physician. Smell and Taste Disorders: A Primary Approach. 
  • Medline Plus. Smell-impaired.
  • NIH Senior Health. Problems with smell.