Smell & Taste Disorders
Smell Disorders
How common are smell disorders?
Our sense of smell helps us enjoy life. We delight in the aromas of our favorite foods or the fragrance of flowers. 
Our sense of smell also is a warning system, alerting us to danger signals such as a gas leak, spoiled food, or a fire. Any loss in our sense of smell can have a negative effect on our quality of life. It also can be a sign of more serious health problems.
Roughly 1–2 percent of people in North America say that they have a smell disorder. Problems with smell increase as people get older, and they are more common in men than women. In one study, nearly one-quarter of men ages 60–69 had a smell disorder, while about 11 percent of women in that age range reported a problem.
Many people who have smell disorders also notice problems with their sense of taste. To learn more about your sense of taste, read the NIDCD fact sheet Taste Disorders.
How does our sense of smell work?
Our sense of smell—like our sense of taste—is part of our chemosensory system, or the chemical senses.
Specialized sensory cells, called olfactory sensory neurons, are found in a small patch of tissue high inside the nose. These cells connect directly to the brain. Each olfactory neuron expresses one odor receptor. Microscopic molecules released by substances around us—whether it’s coffee brewing or a pine forest—stimulate these receptors. Once the neurons detect the molecules, they send messages to our brain, which identifies the smell. (Because there are more smells in the environment than there are receptors, a given molecule may stimulate a combination of receptors. This response is registered by the brain as a particular smell.)
Smells reach the olfactory sensory neurons by way of two pathways. The first pathway is through your nostrils. The second pathway is through a channel that connects the roof of the throat region to the nose. When we chew our food, aromas are released that access the olfactory sensory neurons through this channel. If the channel is blocked, such as when our noses are stuffed up from a cold or flu, odors cannot reach the sensory cells and much of our ability to enjoy a food’s flavor is lost. In this way, our senses of smell and taste work closely together. Without the olfactory sensory neurons, familiar flavors such as chocolate or oranges would be hard to distinguish. Some people who go to the doctor because they think they’ve lost their sense of taste are surprised to learn that they have a smell disorder instead.
Our sense of smell is also influenced by something called the common chemical sense. This sense involves thousands of nerve endings, especially on the moist surfaces of the eyes, nose, mouth, and throat. These nerve endings help us sense irritating substances such as the tear-inducing power of an onion or the refreshing cool of peppermint.
What are the smell disorders?
People who experience smell disorders either have a loss in their ability to smell or changes in the way they perceive odors. Hyposmia is a reduced ability to detect odors. Anosmia is the inability to detect odors at all. People who experience changes in how they sense odors may notice that familiar odors are distorted or that something that normally smells pleasant now smells foul. Other people may sense an odor that isn't present at all.
What causes smell disorders?
Smell disorders have many causes, with some more obvious than others. Most people who develop a smell disorder have experienced a recent illness or injury. Common causes of smell disorders are:
- Sinus and other upper respiratory infections
- Polyps in the nasal cavities
- Frontal head injuries
- Hormonal disturbances
- Dental problems
- Exposure to certain chemicals, such as insecticides and solvents
- Numerous medications, including some common antibiotics and antihistamines
- Radiation associated with the treatment of head and neck cancers
- Aging
- Other health issues that affect the nervous system, such as Parkinson’s disease or Alzheimer’s disease
In 2009, the U.S. Food and Drug Administration warned consumers to stop using several popular cold remedies because they could result in the loss of smell. Smoking also can interfere with our sense of smell.
How are smell disorders diagnosed?
Both smell and taste disorders are treated by an otolaryngologist, a doctor who specializes in diseases of the ear, nose, throat, head, and neck. Some tests are designed to measure the smallest amount of odor that patients can detect. Another common test consists of a booklet of sheets that contain tiny beads filled with specific odors. Patients are asked to scratch each sheet and identify the odor.
An accurate assessment of your smell disorder will include, among other things, a physical examination of your ears, nose, and throat; a review of your health history, such as exposure to toxic chemicals or trauma; and a smell test supervised by a health care professional.
Are smell disorders serious?
Like all of our senses, our sense of smell plays an important part in our lives. The sense of smell often serves as a first warning signal, alerting us to the smoke of a fire, spoiled food, or the odor of a natural gas leak or dangerous fumes.
When smell is impaired, some people change their eating habits. Some may eat too little and lose weight while others may eat too much and gain weight. Food becomes less enjoyable and people may use too much salt to improve the taste. This can be a problem for people with certain medical conditions, such high blood pressure or kidney disease. In severe cases, loss of smell can lead to depression.
Problems with our chemical senses may be a sign of other serious health conditions. A smell disorder can be an early sign of Parkinson’s disease, Alzheimer’s disease, or multiple sclerosis. It can also accompany or be a sign of obesity, diabetes, hypertension, and malnutrition. If you are experiencing a smell disorder, talk with your physician.
Can smell disorders be treated?
Many types of smell disorders are curable, and for those that are not, counseling is available to help people adjust to the problem.
Diagnosis by a doctor is important to identify and treat the underlying cause of a potential smell disorder. If your problem is caused by certain medications, talk to your doctor to see if lowering the dosage or changing that medicine may reduce its effect on your sense of smell. Surgery to remove nasal obstructions such as polyps can restore airflow. Some people recover their ability to smell when the illness causing their olfactory problem is resolved. Occasionally, a person may recover his or her sense of smell spontaneously.
Taste Disorders
How common are taste disorders?
Many of us take our sense of taste for granted, but a taste disorder can have a negative effect on a person’s health and quality of life. If you are having a problem with your sense of taste, you are not alone. More than 200,000 people visit a doctor each year for problems with their chemical senses, which include taste and smell.
The senses of taste and smell are very closely related. Some people who go to the doctor because they think they have lost their sense of taste are surprised to learn that they have a smell disorder instead. To learn more about your sense of smell, read the NIDCD fact sheet Smell Disorders.
How does our sense of taste work?
Our ability to taste occurs when tiny molecules released by chewing, drinking, or digesting our food stimulates 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 tip of your tongue contain taste buds. At birth, we have about 10,000 taste buds, but after age 50, we may start to lose them.
When the taste cells are stimulated, they send messages through three specialized taste nerves to the brain, where specific tastes are identified. Each taste cell expresses a receptor, which responds to one of at least five basic taste qualities: sweet, sour, bitter, salty, and umami. Umami, or savory, is the taste we get from glutamate, which is found in chicken broth, meat extracts, and some cheeses. 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.
Taste quality is just one aspect of how we experience a certain food. Another chemosensory mechanism, called the common chemical sense, 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 give rise to the sensations of heat, cold, and texture. When we 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 us know whether we are eating a pear or an apple.
Many people who think they have a taste disorder actually have a problem with smell. When we chew, aromas are released that activate our sense of smell by way of a special channel that connects the roof of the throat to the nose. If this channel is blocked, such as when our noses are stuffed up by a cold or flu, odors cannot reach sensory cells in the nose that are stimulated by smells. As a result, much of our enjoyment of flavor is lost. Without smell, foods tend to taste bland and have no flavor.
What are the taste disorders?
The most common taste disorder is phantom taste perception; that is, a lingering, often unpleasant taste even though you have nothing in your mouth. We also can experience a reduced ability to taste sweet, sour, bitter, salty, and umami, a condition called hypogeusia. Some people cannot detect any tastes, which is called ageusia. True taste loss, however, is rare. Most often, people are experiencing a loss of smell instead of a loss of taste.
In other disorders of the chemical senses, an odor, a taste, or a flavor may be distorted. Dysgeusia is a condition in which a foul, salty, rancid, or metallic taste sensation will persist in the mouth. Dysgeusia is sometimes accompanied by burning mouth syndrome, a condition in which a person experiences a painful burning sensation in the mouth. Although it can affect anyone, burning mouth syndrome is most common in middle-aged and older women.
What causes taste disorders?
Some people are born with taste disorders, but most develop them after an injury or illness. Among the causes of taste problems are:
Upper respiratory and middle ear infections
Radiation therapy for cancers of the head and neck
Exposure to certain chemicals, such as insecticides and some medications, including some common antibiotics and antihistamines
Head injury
Some surgeries to the ear, nose, and throat (e.g., third molar—wisdom tooth—extraction and middle ear surgery)
Poor oral hygiene and dental problems
How are taste disorders diagnosed?
Both taste and smell disorders are diagnosed by an otolaryngologist, a doctor of the ear, nose, throat, head, and neck. An otolaryngologist can determine the extent of your taste disorder by measuring the lowest concentration of a taste quality that you can detect or recognize. You may also be asked to compare the tastes of different substances or to note how the intensity of a taste grows when a substance’s concentration is increased.
Scientists have developed taste testing in which the patient responds to different chemical concentrations. This may involve a simple “sip, spit, and rinse” test, or chemicals may be applied directly to specific areas of the tongue.
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 health care professional.
Are taste disorders serious?
Taste disorders can weaken or remove an early warning system that most of us take for granted. Taste helps us detect spoiled food or liquids and, for some people, the presence of ingredients to which they are allergic.
Loss of taste can create serious health issues. A distorted sense of taste can be a risk factor for heart disease, diabetes, stroke, and other illnesses that require sticking to a specific diet. When taste is impaired, a person may change his or her eating habits. Some people may eat too little and lose weight, while others may eat too much and gain weight.
Loss of taste can cause us to eat too much sugar or salt to make our food taste better. This can be a problem for people with certain medical conditions, such as diabetes or high blood pressure. In severe cases, loss of taste can lead to depression.
Loss of taste and smell can also be a sign of certain degenerative diseases of the nervous system, such as Parkinson’s disease or Alzheimer’s disease. If you are experiencing a taste disorder, talk with your physician.
Can taste disorders be treated?
Many types of taste disorders are curable. For those that are not, counseling is available to help people adjust to their problem.
Diagnosis by an otolaryngologist is important to identify and treat the underlying cause of your disorder. If a certain medication is the cause, stopping or changing your medicine may help eliminate the problem. (Do not stop taking your medications unless directed by your doctor, however.) Some people, notably those with respiratory infections or allergies, regain their sense of taste when these conditions are resolved. Often, the correction of a general medical problem also can correct the loss of taste. Occasionally, a person may recover his or her sense of taste spontaneously. Proper oral hygiene is important to regaining and maintaining a well-functioning sense of taste.
If you lose some or all of your sense of taste, there are things you can do to make your food taste better:
Prepare foods with a variety of colors and textures.
Use aromatic herbs and hot spices to add more flavor; however, avoid adding more sugar or salt to foods.
If your diet permits, add small amounts of cheese, bacon bits, butter, olive oil, or toasted nuts on vegetables.
Avoid combination dishes, such as casseroles, that can hide individual flavors and dilute taste.
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