Smell and Taste Disorders

Overview

Your senses of smell and taste are closely connected — and both play a bigger role in your daily life than you might realize. Many people who have smell disorders also notice problems with their sense of taste.

How Smell Works

Your ability to smell comes from specialized cells called olfactory sensory neurons, found in a small area high inside the nose. Microscopic molecules released by substances around you, whether it’s coffee brewing or pine trees in a forest, stimulate odor receptors. Once the neurons detect the molecules, they send messages to your brain, which identifies the smell.

Smells reach the olfactory sensory neurons through two pathways. The first is through your nostrils. The second is through a channel that connects the roof of the throat to the nose. Chewing food releases aromas that access the olfactory sensory neurons through this second channel. If the channel is blocked — such as when your nose is stuffed up by a cold or flu — odors can’t reach the sensory cells. As a result, you lose much of your ability to enjoy the flavor of food. Also, familiar flavors such as chocolate or oranges could be hard to identify.

You can also watch a video on how smell works: Journey of Smell to the Brain | NIDCD.

How Taste Works

Your ability to taste comes from tiny molecules released when you chew, drink, or digest food; these molecules stimulate special sensory cells in the mouth and throat. These taste cells, or gustatory cells, are clustered within the taste buds of the tongue and roof of the mouth, and along the lining of the throat. Many of the small bumps on the tongue contain taste buds. Adults typically have several thousand taste buds, which are continuously renewed throughout life. Taste buds and taste bud function may gradually decline with age, though the changes are highly variable across individuals.

When the taste cells are stimulated, they send messages through three specialized cranial nerves to the brain, where specific tastes are identified. Taste cells have receptors that respond to one of at least five basic taste qualities: sweet, sour, bitter, salty, and umami (savory). A common misconception is that taste cells that respond to different tastes are found in separate regions of the tongue. In humans, the different types of taste cells are scattered throughout the tongue.

How We Sense Coolness and Heat

Taste quality is just one way that you experience a certain food. Another chemosensory mechanism, called the common chemical sense (chemesthesis), involves thousands of nerve endings, especially on the moist surfaces of the eyes, nose, mouth, and throat. These nerve endings give rise to sensations such as the coolness of mint and the burning or irritation of chili peppers. Other specialized nerves create the sensations of heat, cold, and texture. When you eat, the sensations from the five taste qualities, together with the sensations from the common chemical sense and the sensations of heat, cold, and texture, combine with a food’s aroma to produce a perception of flavor. It is flavor that lets you know whether you are eating a pear or an apple.

Signs and Symptoms

Smell Disorders

People who have a smell disorder either have a decrease in their ability to smell or changes in the way they perceive odors, such as the following:

• Hyposmia is a reduced ability to detect odors.
• Anosmia is the complete inability to detect odors; in rare cases, someone may be born without a sense of smell, a condition called congenital anosmia.
• Parosmia is a change in the normal perception of odors, such as when the smell of something familiar is distorted, or when something that normally smells pleasant now smells foul.
• Phantosmia is the sensation of an odor that isn’t there.

Taste Disorders

People who have a taste disorder either have a decrease in their ability to taste or changes in the way they perceive tastes, such as the following:

• Dysgeusia is a distorted sense of taste, such as a persistent foul, salty, rancid, or metallic taste in the mouth; sometimes accompanied by Burning Mouth Syndrome, a painful burning sensation in the mouth.
• Hypogeusia is a reduced ability to taste sweet, sour, bitter, salty, and umami.
• Ageusia is the complete inability to taste anything.
• Phantom taste perception is a lingering, often unpleasant taste even when nothing is in the mouth.

Related Health Effects

Smell and taste disorders can affect your health in several ways.

Nutrition and Weight

When smell is impaired, some people change their eating habits — eating too little and losing weight or eating too much and gaining weight. If you have lost some of your sense of taste and smell, you may not eat enough nutritious foods to stay healthy, which can lead to unintentional weight loss or gain, or malnutrition. On average, people with smell dysfunction eat a less healthy diet, with more saturated fats and added sugars. A distorted sense of taste may make it harder to follow diets required for certain health conditions. Because of this, smell and taste disorders may increase risk of obesity, diabetes, hypertension, heart disease, stroke, and malnutrition.

Mood and Mental Health

Long-term loss of smell can affect your mood and quality of life. In severe cases, loss of smell can be associated with depression, loneliness, and social isolation.

Safety Risks

Your senses of smell and taste often serve as a first warning signal, alerting you to the smoke of a fire, spoiled food, the presence of food you’re allergic to, or the odor of a natural gas leak or dangerous fumes. When smell is impaired, these safety signals may go undetected.

Neurological Conditions

A smell disorder can be an early sign of Parkinson’s disease, or Alzheimer’s disease, and may also occur in multiple sclerosis and other neurological conditions. Olfactory loss often precedes the motor symptoms of Parkinson’s disease by several years and has been linked to cognitive decline and future Alzheimer’s disease diagnoses in longitudinal studies.

Causes and Risk Factors

Some people are born with a smell or taste disorder. Most people who develop them have experienced a recent illness or injury. Common causes include:

• Sinus, middle ear, and other upper respiratory infections
• Viral infections, including COVID-19, can cause sudden smell and taste loss
• Nose, facial, or head injury
• Poor oral hygiene, infections of the teeth or gums, or reduced saliva flow
• Exposure to certain chemicals, such as insecticides and solvents
• Numerous medicines, including some common antibiotics and antihistamines
• Radiation for treatment of head and neck cancers
• Surgery to the ear, nose, and throat (such as middle ear surgery) or extraction of the third molar (wisdom tooth)
• Aging
• Smoking
• Heavy alcohol use
• Nasal polyps or other growths in the nasal cavities
• Hormonal disturbances
• Conditions that affect the nervous system, such as Parkinson’s disease or Alzheimer’s disease

Prevention Guidance

Oral hygiene

Brushing your teeth, flossing, and using mouthwash regularly can help prevent gum disease and infections that change the way food tastes.

Allergies

Try to avoid things you’re allergic to, such as pollen or pets. If you cannot avoid your triggers, talk to your doctor about ways to manage your allergies.

Smoking and alcohol

Reducing or stopping smoking and alcohol use may help preserve your sense of taste and smell.

Home Safety Tips

Because smell disorders can affect your safety, it’s important to take steps to protect yourself — especially if your sense of smell has diminished.

• Burnt food. Use a timer to prevent food from burning, since a diminished sense of smell may make it harder to notice.
• Smoke. Check your smoke detectors regularly to make sure they work. People who have hearing loss or cognitive impairment may want to install special smoke alarms that use lights or vibration.
• Gas leaks. Make sure you have a natural gas and carbon monoxide detector in your home.
• Spoiled food. Check expiration dates and throw out food that’s been in the refrigerator or freezer too long. Learn more about how to keep food safe.
• Household chemicals. Always store them properly.

Diagnosis

Both smell and taste disorders are most often diagnosed by an otolaryngologist (a doctor who specializes in diseases of the ear, nose, throat, head, and neck, sometimes called an ENT), though primary care clinicians and other specialists can also assess and refer.

When evaluating smell or taste problems, your doctor may ask:

• Can you smell anything at all?
• Can you taste any food?
• When did you first notice the problem?
• Is the problem getting worse?
• Have you been told that you have allergies or chronic sinus problems?
• What medicines do you take?

Diagnosing Smell Disorders

An accurate assessment of a smell disorder includes a physical examination of the ears, nose, and throat; a review of your health history, such as exposure to toxic chemicals or injury; and a smell test supervised by a healthcare professional.

There are several common ways to test smell:

• Some tests measure the smallest amount of odor a person can detect.
• Another common test uses a paper booklet such as the University of Pennsylvania Smell Identification Test (UPSIT) or SCENTinel with pages containing tiny beads filled with specific odors. People scratch each page and identify the odor. If they can’t smell the odor or identify it incorrectly, it could indicate a smell disorder.
• Odor-pen tests such as Sniffin’ Sticks can measure how well you can identify odors, tell odors apart, and the lowest amount of odor you can detect.

Diagnosing Taste Disorders

Scientists have developed taste tests that measure the lowest amount of taste you can detect and identify. This may involve a simple “sip, spit, and describe the taste” test. Alternately, chemicals with different concentrations may be applied directly to the tongue and you may be asked to compare tastes of different substances or different concentrations of substances.

An accurate assessment of your taste loss will include, among other things, a physical examination of your ears, nose, and throat; a dental examination and assessment of oral hygiene; a review of your health history; and a taste test supervised by a healthcare professional.

Treatment and Management

Treatment depends on what is causing the smell or taste disorder.

• Side Effect of Medicine: If a medicine is the cause, your doctor may consider changing the dose or switching you to an alternate. Do not stop taking medicine without first discussing it with a doctor.
• Nasal obstructions: If nasal polyps are restricting airflow in your nose, you might need medicine (such as topical or oral corticosteroids) or surgery to reduce or remove them and help restore your sense of smell.
• Medical conditions: If a medical condition is the cause, your doctor will treat the condition or refer you to another doctor who can. Often, treating the medical problem will eliminate the taste disorder. For example, if you’ve lost your sense of taste because of respiratory infections or allergies, you should regain your taste when those conditions resolve.
• Cancer treatment: Your sense of smell and taste may return when treatment stops. The NIH National Cancer Institute offers tips on managing cancer treatment side effects that can affect taste.
• Salivary gland issues: Your doctor can help diagnose and treat salivary gland conditions and other common causes of taste loss.
• Oral Hygiene: Brushing or scraping the tongue and a professional cleaning of the teeth and gums to remove calculus have been shown to improve taste.
• Olfactory training: For some people with smell loss, especially after viral illness, repeatedly smelling a set of distinct odors (such as rose, eucalyptus, lemon, and clove) twice daily over several months (“olfactory training”) may help improve olfactory function.

Spontaneous Recovery

Some people recover their ability to smell when they recover from the illness causing their loss. Some people recover their sense of smell spontaneously, for no obvious reason. Some people with a taste disorder will get their taste back without any treatment.

Living With a Taste or Smell Disorder

Talk to your doctor. If the foods you enjoy don’t smell or taste the way you think they should, talk to your doctor. There are likely ways to help solve the problem, and if not, a doctor can help you cope.

Consider counseling. If your smell disorder can’t be successfully treated, you might want to seek counseling to help you adjust. Living with long-term smell or taste loss can be isolating, and talking to a mental health professional or joining a patient support community can help.

Consider patient-led organizations for support. Patient-led organizations such as the Smell and Taste Association of North America (STANA) offer education, peer support, and advocacy for people living with chemosensory disorders.

Make food more appealing. If you lose some or all your sense of taste or smell, there are steps you can take to make food more enjoyable and maintain good nutrition.

• Prepare foods with a variety of colors and textures.
• Try eating brightly colored vegetables such as carrots, sweet potatoes, broccoli, and tomatoes.
• If your diet allows, flavor your food with a little olive oil, nuts, or fresh herbs like sage, thyme, or rosemary (if you have taste but not smell loss).
• Season your food with mustard, hot peppers, onions, garlic, ginger, different spices, or lemon or lime juice.
• Avoid dishes that combine different foods, such as casseroles, which can hide individual flavors and dilute taste.

Watch your nutrition. When food tastes bland, you might consider adding more flavor through herbs, spices, or citrus. Adding more salt or sugar may not be a healthy solution, especially if you have medical problems such as high blood pressure or diabetes.

Work with a nutritionist. Work with your doctor or a nutritionist to identify other ways you can adjust your diet to improve the taste of your food.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on smell and taste disorders.

Community Support

• Smell and Taste Association of North America
• Mass General Eye and Ear
• Monell Center: Advancing Discovery in Taste and Smell

Note: This resource list is for informational purposes only. It is not comprehensive, and an organization’s inclusion does not constitute an endorsement by NIH. 

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.

NIH supports basic and clinical research on the causes, diagnosis and treatment of smell and taste disorders. These scientists are working to:

• Understand and promote the regeneration of sensory nerve cells.
• Understand the effects of the environment (such as gasoline fumes, chemicals, and extremes of humidity and temperature) on smell and taste.
• Prevent the effects of aging on smell and taste function.
• Develop new diagnostic tests for taste and smell disorders.
• Understand associations between smell disorders and changes in diet and food preferences in older adults or among people with chronic illnesses.

The NIH has also established a National Smell and Taste Center to provide clinical training, clinical care, and research on normal and disordered smell and taste.

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.