Hyposmia is the loss of sense of smell. There are many potential causes for hyposmia, including other health conditions, medication, and head injuries.
When people think of the taste or flavor of food, they are considering a combination of sensations, with only some coming from the tongue and taste buds.
The sense of smell contributes greatly to the flavor of foods, as many people will have noticed after a bad cold when food seems to lose its taste. This is why some people with hyposmia think they are suffering from a taste problem when only their sense of smell is affected.
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Causes of hyposmia
People can lose some of their ability to smell for several reasons. Possible causes of hyposmia include:
- head injuries
- infections, such as the flu
- small growths in the nose or sinuses, known as polyps
- deviated nasal septum
Chronic sinus problems, including chronic sinusitis, have also been linked to reductions in the sense of smell.
When the sinuses remain blocked, swollen, and filled with mucus for more than 12 weeks despite treatment, the ongoing inflammation may damage the cells that allow people to smell.
Doctors specializing in conditions affecting the nose maintain that reducing this inflammation can improve the sense of smell.
At least 250 different medications also affect the sense of taste or smell, and some of these drugs can cause hyposmia. They include:
- antibiotics, such as ampicillin and tetracycline
- antidepressants, such as amitriptyline
- antihistamines, such as loratadine
Additional contributors to hyposmia include long-term exposure to certain chemicals, tobacco smoking, or use of recreational drugs, such as cocaine.
Age is another leading factor in a partial loss of the sense of smell. According to the American Academy of Otolaryngology - Head and Neck Surgery, the sense of smell is at its best when people are between 30 and 60 years old. It begins to get weaker after that. Hence, a degree of hyposmia is common in older adults, affecting 39 percent of those over the age of 80.
The loss of sense of smell may be an indication of other health conditions, such as Parkinson's disease or type 1 diabetes.
Hyposmia can also be a sign of other health problems, including:
- Parkinson's disease
- multiple sclerosis (MS)
- Alzheimer's disease
- type 1 diabetes
- high blood pressure
Most people who have hyposmia will not develop Parkinson's disease. However, the majority of people who have Parkinson's disease, which is a condition of the central nervous system, lose some of their ability to smell.
Due to the link between hyposmia and Parkinson's disease, a test for reduced sense of smell could potentially lead to earlier diagnosis of the disease.
In the case of one of the more common forms of dementia in the U.S, the possibility of using a smell test to screen for early diagnosis is also the subject of ongoing research.
MS is yet another condition that has been associated with hyposmia. A study of people with MS found that 40 percent of its participants had at least a partial loss of their sense of smell. The greater their MS-related disabilities, the more difficulty they had identifying a specific scent.
Multiple studies have found that people with type 1 diabetes can have trouble detecting and distinguishing scents. The more discomfort they had due to diabetic nerve damage, called peripheral neuropathy, the more problems they had with their sense of smell.
Although cancers of the head and neck might not affect the sense of smell directly, irradiation treatment for these conditions can cause some degree of hyposmia.
How might hyposmia progress?
Hyposmia often improves without treatment, particularly if it is caused by seasonal allergies or an infection of the respiratory tract. A person who notices a reduced sense of smell when they have a cold, usually find it returns to normal a few days or weeks after they recover.
When hyposmia is caused by a head injury or a significant inflammatory injury to the cells involved in smell, a complete recovery may not be possible, even with surgery.
However, some medications and retraining of the sense of smell have proven helpful for people with hyposmia.
What is anosmia?
Anosmia is the medical term for complete loss of the sense of smell.
Some people are born with this condition, when it is referred to as congenital. However, it is most frequently caused by head injuries or problems with the nasal passages. These problems can include chronic inflammatory nasal or sinus disease, or a severe viral infection of the upper respiratory tract.
According to the Anosmia Foundation, however, as many as 22 percent of cases of anosmia are idiopathic. This means that no cause can be found for the loss of smelling ability.
When to see a specialist
A medical professional can diagnose hyposmia by physically examining the nasal passages and sinuses.
People have a surprisingly sophisticated sense of smell that can detect from 10,000 to 100 billion different odors. This sensory information plays an important role in supporting a person's quality of life and physical safety.
Enticing aromas encourage people to eat, and nasty smells warn of fire, toxic chemicals or bad food.
Smells also create connections with people and places, say, with the scent of a certain perfume or memories of the seaside or countryside.
When hyposmia limits these abilities, a person must get help immediately to avoid isolation and threats to their physical well-being.
If individuals notice a drop in their ability to smell, they should see a specialist, particularly if the onset of hyposmia is sudden and severe.
The loss of smell can respond well to treatment, especially if it is soon after the problem begins.
Treatment and outlook
Diagnosis and treatment usually begins with a physical examination and check of a person's medical history, especially of upper respiratory problems. A doctor will look at the nasal passages, sinuses, and surrounding structure.
When more detailed images are needed, a nose and throat specialist called an otolaryngologist may conduct a procedure called nasal endoscopy.
In this short procedure, a long thin tube with a camera is inserted into the patient's nose to look at the nasal and sinus cavities.
A doctor will be looking for signs of swelling, bleeding, pus, and possible cancer tumors. Also, they will be on the lookout for other physical blockages that could account for the loss of smell, such as polyps, enlarged nasal structures, or a deviated nasal septum.
If these tests are negative, an MRI scan may be done to look for problems in the areas that detect smells and the brain.
A scratch and sniff test, or tests with "Sniffin' Sticks," helps physicians determine whether someone has anosmia or hyposmia. In cases of hyposmia, these tests will measure the extent of the loss of smell.
On the whole, medication and surgery are used to treat hyposmia. Surgery can be an effective treatment when nasal polyps, a deviated septum, or other problems that can be removed or repaired, are causing the loss of smell.
Medications, such as steroids and antihistamines, may be used to calm the inflammation when allergies or respiratory infections are the cause.
People with hyposmia need to take care to make sure their reduced smelling ability does not cause additional health and safety problems.
It is important to ensure that the loss of smell does not lead to under- or over-eating.
People should make sure that smoke and gas detectors are installed in the household and are well-maintained. To limit the possibility of undetected gas leaks, which are often found by smell initially, people could consider switching from gas to electric appliances.
Using caution when working with potentially toxic household chemicals and keeping a close eye on food expiration dates is also advised.