Many things can cause smell loss, such as sinus disease
(chronic rhinosinusitis), head trauma, the common cold, and aging. Sometimes there is no explanation at all.
Smell loss happens when there is a blockage of airflow getting to the nerves responsible for detecting odors, direct damage to the nerves, or direct damage to the areas of the brain where the sense of smell is processed. Often, a loss of smell is noticed when you have difficulty tasting food. This is because flavor is a combination of smell and taste. With a smell loss, the taste of food is reduced to a very bland sensation.
Besides the loss of sense of smell, some patients experience a distorted smell, or a “phantom” smell (an odor that other people can’t smell).
Your physician will evaluate the smell loss through an extensive discussion of your history and by an endoscopic examination of your nasal cavity. A smell test may also be performed. Depending on the results, further testing such as an MRI or CT scan may be needed.
Unfortunately, there are not many therapies available to patients with smell loss. In cases where the smell loss is caused by chronic rhinosinusitis, medication or surgery may be helpful. Oral steroids might also help in treating certain forms of smell loss, but they may only provide a short-term benefit.
A recently described therapy has shown some benefit in people with smell loss that does not involve medication. This technique, known as olfactory training, involves repetitive smelling of four odors, twice-a-day for at least three months and has provided improvement in some patients with diminished ability to smell.
Sometimes, patients believe they have taste loss, when it is actually a loss of smell. This is because the flavor of food is a combination of smell and taste.
But there are some patients with a true taste loss, though it is much less common. It is difficult to have a complete taste loss, because taste is processed by the surface of the tongue and by three different nerves. It is more common to have decreased or altered taste (often described as “metallic”) than a total taste loss.
True taste loss has many causes, including infection, central brain disorders, nutritional deficits, or complications in surgery of the mouth or ear.
An important part of evaluating a taste loss is to first make sure that it is not smell loss. Once smell loss is ruled out, we evaluate the taste loss through an extensive discussion of your history and an endoscopic examination of your nasal cavity. We may also administer a taste test. Depending on the results, further testing such as an MRI or CT scan may be needed.
The ability to treat a taste loss depends on the ability to identify the cause. If infection is the underlying cause, it can be treated with antibiotic or antifungal medications. In many cases, the cause of taste loss is unknown.