Loss of Smell and Taste
Have you noticed the pleasure of eating has gone away? That often happens with a loss of smell and taste. You are not alone. More than 200,000 people each year visit an ENT doctor with smell and taste disorders. When smell and taste are impaired, we eat poorly, socialize less and, as a result, feel worse.
Anatomy of olfaction
Smell, called olfaction, is the ability to sense and identify a substance by detecting tiny amounts of the substance that evaporate and produce an odor.
In humans, the sense of smell differs from the other senses (sight, hearing, and taste) in its directness. People actually smell microscopic tidbits or chemicals of a substance that have evaporated and made their way through the nostrils into the nasal cavity. In the roof of the nasal cavity is a section of mucous membrane called the olfactory epithelium. It covers an area about the size of a postage stamp.
The olfactory epithelium contains about 50 million odor-sensitive receptor cells (chemoreceptors) that are connected to the olfactory nerves. The olfactory receptors have long olfactory hairs that protrude outward from the epithelium. Beneath the olfactory epithelium lie olfactory glands that produce mucus that covers the epithelium and bathes the olfactory hairs. The mucus keeps the area moist and clean and prevents the buildup of potentially harmful or overpowering chemicals.
click to enlarge image
click to enlarge image
Anatomy of taste buds
Your tongue has somewhere around 10,000 taste buds. But there are no more than 6 distinctive tastes: salty, sour, sweet, bitter, umami and possibly fatty acids.
The front of the tongue contains the sweet taste buds. The tip of our tongue is particularly useful for enjoying frosting, sugar, and chocolate.
Sour tastes, such as lemons, limes, and sour candy, stimulate the specialized receptors on the sides of our tongue.
Then, way in the back of your tongue has the taste buds for all those bitter tastes, such as a rotten piece of fruit.
And finally, all around the main part of your tongue are the taste buds for experiencing anything salty. The dominance of the salt receptors should not be a surprise.
How we taste
The 10,000 different scents which humans usually recognize as 'tastes' are often actually 'flavors'. People are actually smelling, not so much tasting their foods. Maybe you have noticed the loss of taste during a cold when you can’t breath well through your nose.
The loss of smell (anosmia) may be gradual or sudden. It can be a partial or complete loss. Some people are born without olfaction and they become used to it, but someone who loses her sense of smell later in life has trouble with everything "tasting like wet cardboard".
When food becomes less appealing, a great pleasure in life may be lost. This can be a difficult challenge in one’s life. It can be the cause of depression.
Loss of olfaction can also be dangerous because it affects one’s ability to smell gas leaks, fire, body odor and spoiled food.
- Upper respiratory tract infection (e.g., sinusitis or the common cold)
- A temporary loss of smell can be caused by a stuffy (blocked) nose or infection.
- A loss of smell that does not get better after a week or two may be caused by the death of olfactory receptor neurons in the nose. This is a shocking experience and hard to believe that a common cold virus could cause this much distress, but it is all too common.
- Nasal polyps
- Aging: This is a gradual deterioration in the olfactory nerves and generally results in a diminished sense of smell.
Less common causes
- Laryngectomy with permanent tracheostomy
- Toxins (especially acrylates, methacrylates and cadmium)
- Head trauma
- Parkinson's Disease
- Alzheimer's Disease
- Esthesioneuroblastoma (an exceedingly rare cancerous tumor)
- Kallmann syndrome
- Absence at birth, usually due to genetic factors (congenital anosmia)
Everyone should be evaluated for this problem because occasionally early intervention can prevent a permanent loss. Also, a progressive loss can be a sign of a more serious medical condition.
- Testing for the presence of normal taste and, more importantly, smell is the cornerstone of diagnosis. A doctor’s office can administer a scratch-n-sniff odor test. But you can test yourself with these common home odorants: coffee, lemon, grape, vanilla and cinnamon.
- You need to have your nasal cavities examined to check for different types of obstruction, such as nasal polyps. Often a fiberoptic endoscope (link) is used to see the deeper parts of the nose.
- An MRI scan or CT scan may be used to evaluate your olfactory nerves, nasal and sinus anatomy and to eliminate the possibility of a tumor.
Since there are several different causes of anosmia, there may be several treatment options.
- Loss of the sense of smell may be temporary, and ability to smell may return spontaneously, especially after colds or viral infections.
- Treatment of underlying disorders, such as antihistamines for allergies or nasal steroids for nasal polyps, may correct loss of the sense of smell.
- Quitting smoking improves the smell function.
- Surgical treatment of chronic sinusitis, nasal polyps, deviated septum or enlarged turbinates can improve airflow and sense of smell .
- Zinc and vitamin A supplements are sometimes recommended, but have proven to be ineffective.
Smell and taste also warn us about dangers, such as fire, poisonous fumes and spoiled foods. click here for a copy of our handout. (available in our patient-only area)