If you’re having trouble detecting strong odors or scents, or you’re struggling to distinguish between different flavors when eating, you may be experiencing anosmia (loss of smell) or hyposmia (partial loss of smell).
Similarly, if you can’t taste flavorful foods, or you notice that some foods taste different or metallic, you may be experiencing ageusia (loss of taste) or hypogeusia (partial loss of taste).
Often, the loss of taste and smell go hand-in-hand, as there is a strong link between the two senses. Odor receptors in your nose and upper throat work together with the taste receptors on your tongue to create the experience of flavor. This is why when you have a stuffy nose, you may notice that foods don’t taste as flavorful.
The sudden loss of taste or smell can be a temporary symptom of common illnesses like the cold or flu, or a long-lasting symptom of a serious injury or chronic condition that disrupts your brain’s ability to process scent and flavor.
What Is Anosmia (Loss of Smell)?
Your sense of smell comes from olfactory sensory neurons, found inside your nasal tissue. Each of these neurons has an odor receptor—when odors are released around you, these receptors detect the smell and send a message to your brain, which interprets and identifies the scent. When any part of this process is interrupted, your sense of smell may be impaired.
This sensory process may be interrupted in three main ways:
- Blockages in the inner lining of the nose: These blockages can prevent smells from reaching your odor receptors.
- Obstructions to the nasal passages: Your odor receptors can’t send messages to the brain if your nasal passage is obstructed.
- Damage to the brain or nerves: An injury or other damage to your brain or nerves can impact your brain’s ability to interpret and identify smells.
If you are suffering from anosmia or hyposmia, you may notice that traditionally strong scents seem muted to you, or you can’t smell odors that others around you can easily detect.
You may also notice that your sense of taste is dulled or absent, or that you have trouble distinguishing between different flavors, because your odor receptors play a role in your ability to taste.
What Is Ageusia (Loss of Taste)?
When you taste something, you’re actually experiencing a two-step chemical reaction involving the mouth, throat, and nose. Your body combines the senses of smell and taste to process the flavor of foods and beverages.
When you consume food, your odor receptors can usually smell the substance before you even put it in your mouth. As you eat or drink, the substance mixes with saliva in your mouth, transporting the taste around the tongue and activating your taste buds. This then sends signals to your brain, and combining both smell and taste, your brain interprets the flavor.
People with ageusia (complete loss of taste) cannot taste sweet, salty, sour, or bitter flavors. People with hypogeusia (reduced sense of taste) can generally taste these flavors, but may not be able to distinguish easily between them. With either ageusia or hypogeusia, you may also experience a metallic sensation in your mouth.
What Causes Loss of Smell and Taste?
There are several factors that might contribute to your loss of smell.
One of the most common causes for a gradual reduction in smell and taste is aging. As many as 75% of people over the age of 80 have an impaired sense of smell. A diminished sense of taste is also quite common because after age 50, our taste buds start to lose their sensitivity and ability to regenerate.
Any viral or bacterial infection that causes a stuffy or runny nose—such as a sinus infection (sinusitis), the common cold, or flu (influenza)—can block odor receptors, resulting in a temporary reduction of smell and taste. This is why food often tastes less flavorful when you have a cold.
When caused by an infection, hyposmia and hypogeusia are usually temporary symptoms; once the infection has cleared, the senses of smell and taste return.
Other causes that can produce a stuffy nose and temporarily and sporadically impact smell and taste include:
- Allergic reactions
- Hay fever (allergic rhinitis)
- Nonallergic rhinitis (chronic congestion or sneezing not related to allergies)
- Upper respiratory infections
Obstructions to the nasal passages can interrupt the process by which odor and taste receptors send messages to the brain. Your nasal passages may be obstructed due to:
- A deviated septum
- Traumatic brain injury (TBI)
- Abscesses such as nasal polyps
In many cases, the loss of taste and smell is temporary and will be recovered if the obstruction is removed. In more serious cases, damage to the nasal cavity or olfactory nerves due to a head injury or traumatic brain injury (TBI) can result in long term or permanent loss or reduction of smell and taste.
More extreme or sudden loss of taste and smell can be caused by other illnesses and conditions that impact the inner lining of the nose, the nasal passage, or the brain. An impaired sense of smell or taste can be a symptom of:
- Certain medications: Some antibiotics, antihistamines, high blood pressure medicines, intranasal zinc products, and nifedipine, have been known to have side effects including loss of smell. In these cases, stopping the medication will generally reverse the effect, although in severe cases, anosmia may become permanent.
- Coronavirus: Loss of taste and smell has also been identified as a potential symptom of coronavirus (COVID-19), which may or may not be accompanied by flu-like symptoms including fever, dry cough, muscle pain, and shortness of breath.
- Radiation therapy: Impaired smell and taste can also be a side effect of radiation therapy for patients undergoing cancer treatment.
- Diabetes: Studies suggest that people with diabetes may be more prone to impaired taste.
- Multiple sclerosis (MS): Because MS impacts the central nervous system, it can cause loss of smell. Some evidence suggests that loss of smell may be an indicator of the severity of this disease.
- Neurodegenerative diseases: People suffering from diseases like Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, or similar conditions may show extreme changes in their food preferences and struggle to identify flavors, indicating possible loss of taste buds and impact to sense of smell. Some researchers posit that decreased sense of smell could be an early indicator of Alzheimer’s or similar causes of neurodegeneration.
- Zinc deficiency: Zinc is an essential trace mineral that our bodies need to support immune system functions and cell regeneration. People who don’t get enough zinc through their diet may experience a diminished sense of taste or smell, among other symptoms.
Diagnosis and Testing
To test for anosmia or hyposmia, your doctor may hold a fragrant substance (such as soap or coffee) under your nostrils and ask you to identify the smell.
If this informal sniff test shows an impaired sense of smell, your doctor may then use a standardized smell test kit for a more complete assessment. The kit may include scratch-and-sniff scent samples that you’ll be asked to identify, or samples of a strongly scented chemical that your doctor will dilute in stages to find the threshold where you can no longer smell the substance.
If the loss of taste and smell is more severe and your doctor has ruled out viral and bacterial infections, your doctor may order an MRI or CT scan to look for any structural issues including a tumor, fracture, or abscess.
Treatment for Loss of Smell and Taste
The primary approach to treating loss of taste and smell is to treat the underlying cause of the issue. There is no direct cure for anosmia and ageusia, though in most cases, treating the cause will return all or part of your sense of smell and taste.
A stuffy or runny nose due to allergies or a viral infection (such as cold and flu) can be treated with over-the-counter medications including decongestants, antihistamines, or steroids to ease inflammation. Easing the stuffiness may help increase your sense of taste and smell in the short term.
Once the body has recovered from the cold or other infection, your senses of smell and taste will fully return. Bacterial sinusitis and throat infections are generally treated with antibiotics. If you are suffering from a sinus infection, treatment may also include steam inhalation to clear the nostrils and ease pressure.
For regular smokers, quitting the habit of smoking tobacco products can result in regaining a sense of taste.
If hyposmia or hypogeusia is the result of aging, a chronic condition, brain trauma, or another cause that permanently alters the senses, there is no treatment to fully regain these senses. In these cases, patients are encouraged to:
- Add more seasonings: Season your food with herbs, spices, vinegar, hot sauce, or other flavorings. Be open to trying new sauces and condiments—if your sense of taste has changed, you may enjoy flavors you didn’t before.
- Try new cuisines: Experiment with different cuisine styles, especially those that have traditionally strong flavors, such as Indian or Mexican cuisines.
- Eat hot foods: The temperature of food can affect our sense of taste. Studies have found that the hotter food is, the more intensely our taste buds react. When possible, heat your meals instead of eating them cold or at room temperature.
- Look for textures: Texture contributes to our enjoyment of food, so try different foods that are crispy, crunchy, or smooth, as this may engage your senses in fresh ways.
- Watch your salt and sugar intake: If you suffer from hyposmia and hypogeusia, you may be drawn to foods high in salt or sugar, as these flavors are often easier to taste. Be mindful not to overdo it with sweet or salty foods in your diet.
When to See a Doctor
If you are experiencing a diminished sense of smell or taste, take note of any recent health issues or changes in your routine, as well as any accompanying symptoms to determine how soon to speak with a doctor. You should see your doctor immediately if you have recently experienced a serious head injury, started a new medication, or are undergoing radiation therapy.
You should also see your doctor if you experience loss of taste or smell in conjunction with the following symptoms:
- Frequent memory loss and confusion
- Sudden difficulty performing otherwise routine tasks
- Challenges with cognitive functions such as speaking and writing
- A sore throat
- Postnasal drip
- Green or yellow nasal discharge
- A fever
- Sudden weight loss, either unexplained or due to difficulty eating
- Open sores or other wounds that won’t heal
If you are worried that you may have coronavirus, chat with a K Health doctor today.
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K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.