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Fever, body aches, and a dry cough are hallmark symptoms of COVID-19; the disease caused by the novel coronavirus. Two other neurological symptoms have been so widely reported that they are sometimes considered the most reliable early indicator of infection: loss of smell (anosmia) and taste (ageusia). But what is the prevalence of this odd side effect? How long does it typically last? Are there other ailments that can cause these symptoms? Read on to find the answers to these questions.

How common is loss of taste and smell from coronavirus?

Around 74% of COVID-19 patients lose their sense of smell, according to one study. Many also lose their sense of taste—likely because taste and aromas are interconnected. In other words, loss of taste and smell is one of the most common symptoms of COVID-19. Often, it’s one of the first noticeable signs that a person may have contracted the coronavirus.

“For decades, physicians have known that respiratory tract viral infections are the most common reason for an acute loss of sense of smell,” says Javeed Siddiqui MD, MPH, the chief medical officer at TeleMed2U. “With the recent pandemic of SARS-CoV-2, a number of epidemiological studies have demonstrated that infection with SARS-CoV-2 is associated with higher rates of anosmia (or loss of smell) then previously seen with other viral infections.”

There is some evidence that loss of taste and smell may be more common with mild to moderate forms of the disease, as opposed to severe cases. Only 26.9% of patients hospitalized with COVID-19 reported anosmia, while 66.7% of COVID-19 infections treated as outpatients reported the symptom, according to UC San Diego Health. Similar percentages were found for loss of taste.

How does coronavirus cause loss of taste and smell?

Scientists are still learning how COVID-19 causes taste and smell dysfunction, though they suspect it involves the nervous system. Researchers at Harvard Medical School believe they have identified the cell types in the olfactory bulb (found in the upper nasal cavity) that are most vulnerable to infection by the SARS-CoV-2 virus, and they recently published their results. “To better understand the rationale for anosmia (or loss of smell), we first need to discuss that the lining of the nose is made up of cells called olfactory epithelium (OE),” Dr. Siddiqui says. “The primary role of the OE is odor detection.” As Dr. Siddiqui explains, the primary site of infection for the virus that causes COVID-19 is the nasopharynx, which is the upper part of the throat, behind the nose.

“We know that SARS-CoV-2 uses the ACE2 receptor (a protein on the surface of many cell types) to gain entry in different cells in the body,” Dr. Siddiqui explains. “The Harvard research group has found that specialized cells within the olfactory epithelium express ACE2 receptors in high frequency. As such the probable reason for loss of smell is due to direct infection of the olfactory epithelium cells by SARS-CoV-2.” In other words, COVID-19 does not directly infect the sensory neurons that carry smells to the brain. It affects how the supporting cells function.

The mechanism by which the SARS-CoV-2 virus causes loss of smell and taste may be complicated, but if you are experiencing a loss of these senses it helps to be aware of the other common symptoms of COVID-19 infection which include:

Fever/chills
Dry cough
Body aches
Shortness of breath
Headache
Sore throat
Loss of appetite

If you experience these symptoms, combined with loss of senses, you should call your healthcare provider.

Other possible causes of loss of taste and smell

Losing your sense of taste and smell does not automatically mean you have COVID-19. A positive test for active infection, or presence of antibodies in your blood are the only true evidence of coronavirus infection. There are many other explanations for loss of these two senses, including:

Viruses: Viruses such as the flu or common cold can cause loss of taste or smell.
Allergies: Nasal allergies and nonallergic rhinitis (nasal stuffiness not caused by allergies or hay fever) can also cause a diminished sense of smell.
Nasal polyps: Large nasal polyps can block the nasal passages causing difficulty breathing, loss of smell, a runny nose, and chronic sinus infections.
Medical conditions: Certain medical conditions can cause a diminished sense of smell including Alzheimer’s disease, multiple sclerosis, and Parkinson’s disease. Hormonal changes, such as during menopause, may also cause changes to taste and smell.
Head injuries or injuries to the nose: A traumatic brain injury can lead to olfactory dysfunction, resulting in loss of taste and smell.
Medications: Certain medications may cause a decreased sense of taste and smell including antibiotics, heart medications, and blood pressure medications. Long term use of intranasal zinc products or decongestants can also cause a loss of taste and smell.
Radiation therapy: Radiation and chemotherapy to the head and neck can cause a weakened sense of taste and smell.

Sense of smell also naturally diminishes as we age. If you’re concerned about loss of taste and smell contact your healthcare provider.

How to safely test your sense of taste and smell

While COVID-19 has a wide range of symptoms, according to the Centers for Disease Control and Prevention (CDC), new loss of taste and smell is often the only symptom that many infected people notice. So, it may be a good idea to periodically test these senses with an at-home technique called the “jellybean test,” as reported by CNN.

Steven Munger, director of the Center for Smell and Taste at the University of Florida, says the test can be performed by holding a jellybean in one hand while completely covering your nose with the other hand; preventing any air flow. Then, you put the jellybean in your mouth and chew it. While still chewing, you remove your hand that was covering your nose and if your sense of smell is intact, you should register the smell and flavor of the jellybean all at once. This is called retro nasal olfaction, and it occurs when odors flow from the back of your mouth up through your nasal pharynx and into your nasal cavity.

If you fail the jellybean test, it could be a sign that you have COVID-19. You can ask your healthcare provider if you need to be tested, or discuss getting a simple smell test. The test involves sniffing different odors at varying concentrations and is usually performed by an ear, nose, and throat specialist or a neurologist. This could also be a sign that you have COVID-19.

How to regain taste and smell (and when to see a healthcare provider)

Losing your sense of taste and smell can feel alarming—what if you can’t smell a gas leak? Or burning food? It has also been associated with depressed mood and anxiety. The good news is that most people with loss of taste and smell from coronavirus should regain it within a few weeks.

“More than two-thirds of [COVID-19] patients tend to recover their sense of taste and smell within three weeks,” says Omid Mehdizadeh, MD, otolaryngologist (ENT) and laryngologist at Providence Saint John’s Health Center in Santa Monica, CA. For some people, however, the loss of these senses may take longer to recover. “One study showed that one-third of patients still reported smell and taste disturbance six to seven weeks out from [COVID-19] infection,” warns Dr. Mehdizadeh. In the process of regaining taste, you may experience dysgeusia, or distortion of your taste, where certain items don’t taste the same way they used to prior to COVID-19.

Signs that you may need to talk to your healthcare provider about loss of taste and smell include:

Prolonged loss of smell (greater than one month)
Headaches
Pain
Thickened nasal drainage
Vision changes
Nose bleeds
Fever

If you’re concerned about how long it’s taking to regain your sense of smell and/or taste after COVID-19, there are some options for treatment. Your primary care provider may also refer you to an otolaryngology specialist.

Smell training

“In cases of post infectious loss of smell, of which COVID-19 is one, smell retraining therapy has been shown to offer some recovery,” says Dr. Mehdizadeh. He recommends smelling potent aromas—or essential oils—such as charred oranges, lemon zest, eucalyptus, and cloves three to four times a day for three to four months. This may help to regenerate the olfactory nerve.

Medication

In addition, Dr. Mehdizadeh says there are also some medications your healthcare provider may prescribe including:

Nasal steroid sprays: Flonase (fluticasone), Nasacort (triamcinolone), Nasonex (mometasone)
Oral steroids: Prednisone, Methylprednisolone (medrol)

According to Dr. Mehdizadeh, “Other medications including Ginkgo Biloba, Zinc, Alpha Lipoic Acid, and Theophylline have been suggested, but their efficacy has not been demonstrated.”

Because COVID-19 is caused by a novel virus (meaning a new strain that has not been previously identified), researchers and scientists are still learning more about its effects on the body every day; including how it impacts our sense of smell and taste. By monitoring these senses, and being aware of any changes, we can help keep ourselves and those around us safe and healthy.