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What causes loss of taste and smell?
A loss of sense of smell and taste is a common symptom of COVID-19, and one that often lingers after people recover from the illness. It can also be caused by other illnesses and structural problems.
A temporary loss of taste and smell can be caused by an obstruction in the nose, like if you have inflammation (causing a stuffy nose) from allergies or a cold or flu. The inflammation prevents smells and odors from reaching the very top of the nasal passages, where olfactory cells, which sense smell, are located.
Long-term loss of taste and smell can be from the olfactory cells or certain nerves that have been damaged through trauma to the head or skull (such as a concussion). There are theories that COVID-19 might damage these nerves, or damage your mucosa (a lining in your nose that helps your nose sense odors).
Normal aging can cause diminished sense of taste and smell, because of a decline in overall brain density and function.
Most people who think they’ve lost taste have actually just lost smell. That’s because smell contributes so much to taste that when the olfactory cells aren’t working properly, you have a hard time tasting food. Many people actually notice the loss of taste first. In some cases, like after having radiation treatment, your taste buds may be affected.
Other causes of taste and smell disturbance include:
- Neurological causes (brain tumor or mass, or a neurodegenerative disease)
- Toxins (such as strong chemicals that are inhaled)
- Congenital disorders
How do we taste and smell?
Taste and smell are two senses that are closely connected, but they work in very different ways. Taste is provided by taste buds, which are on the surface of your tongue and tell you if something you’re eating is salty, sweet, bitter, or sour.
Smell, on the other hand, is provided by olfactory cells, which are on the roof of your nasal passage. They not only identify odors, but also flavors. Because of that, olfactory cells play a huge part in how you taste food.
Some much less common causes include nasal masses, a history of head trauma (like a concussion), or even neurologic disorders (like Parkinson’s disease). For this reason, it is important that everyone who has a persistent change in their taste or smell be fully evaluated by a physician. —Dr. David Lee
How long does it take to recover?
Taste and smell most often return when the cause is addressed, for example, you recover from a cold or allergy season ends. If your loss of taste and smell is because olfactory nerves were damaged, you can recover in a period of weeks to months (the cells actually heal themselves in that time).
In a small percentage of people, these cells are unable to fully recover, and the sense of smell may not completely return. This can significantly affect quality of life, with many people reporting loss of interest in food or drink and even being less aware of their own hygiene, according to a study in the journal European Archives of Oto-Rhino-Laryngology.
For the vast majority of patients, a loss of taste or smell is not permanent. The best treatment is time—simply waiting for the body to heal itself. There should be at least some return of your taste or smell within weeks to months after the onset. —Dr. Lee
Does everyone with COVID-19 lose the sense of taste and smell?
While losing your taste and smell are two of the most well-known signs of COVID-19, it happens to less than half of people who contract the disease. If you have a mild form of the disease, you’re much more likely to lose your sense of taste and smell than if you have a moderate or severe form.
For those who do notice a decrease in their ability to taste or smell, research in the Journal of Internal Medicine found that 95 percent will completely regain it within 6 months.
Tips to regain sense of smell
If your smell doesn’t come back right away, you might want to try one of the following techniques to help it return.
Smell retraining therapy
This is the most promising of all the methods known to help bring back smell. The idea is simple: Treat the cells that sense odors like a muscle group, and “exercise” them every day. You take a set of 10 to 15 very strong smells that you would easily recognize (like coffee, eucalyptus, oranges, or chocolate) and deeply inhale them for 20 seconds, twice a day, for 3 months or longer. While this sounds strange, it has been shown in studies like this one from JAMA Insights to improve smell in people who have lost it for months or even years.
Several very promising studies show that smell retraining therapy, over time, can rehabilitate the sense of smell by retraining the brain to recognize scents and odors. —Dr. Lee
If your loss of smell is because of an infection, an oral or nasal steroid can decrease inflammation in the nasal passages, helping your sense of smell come back sooner. This is true for common illnesses like a cold and allergies but also for COVID-19.
There are no other medications that have been consistently shown to bring back smell, but there are some with mixed reviews. This includes phosphodiesterase inhibitors (like sildenafil, theophylline, or caffeine) and intranasal sodium citrate. Talk to your doctor about whether any of these are an option.
Tips to getting taste buds back
For the most part, people who think they’ve lost their sense of taste actually have an issue with their smell. That said, there are some treatments used in the uncommon situation where it’s truly a lost sense of taste.
If you aren’t producing enough saliva, your taste buds won’t work properly, causing a loss of taste. If you’re not producing enough saliva, you may feel like your mouth is always dry. This can happen during radiation treatment, but it can also happen in people who aren’t undergoing radiation. Whatever the cause, staying hydrated is an easy way to try to bring back your sense of taste.
Taste buds need zinc to function normally. While zinc deficiency is uncommon in the U.S., research shows that zinc supplements can help people with taste issues. Some medications may cause a zinc deficiency too, so let your doctor know about your loss of taste in case it might be a drug side effect.
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