The two most common causes of a loss of smell are allergies or some kind of injury to the nerve tissue from a viral upper respiratory infection. Patients who lose their sense of smell as a result of a respiratory infection will generally be able to date the time of their smell loss to the same time as the respiratory infection they experienced. In general, these tend to be older patients, and the loss of smell that they have incurred is more typically partial than total in nature.
Unfortunately, there is no effective treatment for this situation because viral damage cannot normally be repaired. While it is possible that some patients will recover their sense of smell over time, these patients are definitely in the minority, and comprise less than 20% of the total number of patients experiencing smell loss. It is however, certainly possible that people who experience temporary smell loss after an upper respiratory infection recover it within a few days of being restored to normal health from the infection.
Smell Loss from Sinuses or Allergies
The other most common cause of smell loss is rhinitis, which is an inflammation that occurs in the nose, nasal polyps, or sinusitis. All three of these are considered to be ongoing processes, in that they recur during the lifetime of the patient, and as such, have an ongoing effect on the sense of smell.
Since this is the case, the development of smell loss tends to be a much more drawn-out process, as opposed to the upper respiratory infection cases, which are more spontaneous in nature. People who are troubled with smell loss due to allergies or sinus problems often report improvements in their sense of smell on a temporary basis, for instance after vigorous exercise, showering, or some other activity which elevates one’s heart rate.
It’s also possible for temporary smell improvements to be experienced when taking corticosteroids, antibiotics, or some other kinds of medication, but, in most cases, the improvement eventually subsides, and the loss of smell returns. It’s fairly common in such cases for there to be accompanying symptoms such as post-nasal drip, problems with breathing through the nose, or nasal allergies. Interestingly, the development of smell loss does not result in a loss of taste, or at least that has not been reported by any significant number of studied patients.
For people who have experienced both an upper respiratory infection and an ongoing process like sinusitis, it will usually be very difficult to pinpoint the time of your smell loss. There is a reason, though, that dating the time of smell loss can be important, because of the two types of smell loss, only sinusitis is treatable and reversible. As previously mentioned, viral damage to the nose cannot be repaired, and that means the sense of smell will also be unlikely to improve for the vast majority of patients.
Treatments for Smell Loss
When a doctor is able to determine whether a patient’s loss of smell was triggered by allergies, there are some treatments which may help recover and restore the sense of smell. Antihistamines, antibiotics, and corticosteroids have all proven to be at least somewhat effective in restoring the sense of smell, because they work to decrease inflammation in the nasal passageways, and these are the primary causes of smell loss in the first place.
For patients who have had some physical damage to the nose, such as a deviated septum or nasal polyps, surgery may also be an option to repair the problem. However, the correlation between surgery and successful restoration of the sense of smell is not strong, so for any specific situation, a patient should discuss surgical options with their doctor.
Patients who have suffered a loss of smell following some kind of severe trauma to the nose or an upper respiratory viral illness, have very few treatment options available to them currently. Corticosteroids are sometimes used to provide benefits for some patients, but the success rate is not particularly promising.
New research has shown that attempting to retrain a person’s sense of smell can achieve modest successes, since it attempts to stimulate the regenerative capabilities of the body’s olfactory network. Part of this therapy involves exposing a patient to familiar odors which are very strong and recognizable, so as to promote the recovery of a sense of smell. The theory behind this is that it helps to rewire that area of the brain which processes smells.
Currently, research is underway to explore other avenues for the restoration of the sense of smell in patients who were thought to have experienced total loss. While medical treatments have not been shown to be universally effective, some patients have experienced small gains in their sense of smell when using phentoxifylline, gabapentin, theophylline, various antidepressants, and some kinds of antibiotics. In the future, it is likely that other treatment approaches will be discovered, and that many more patients will be able to cover some sense of smell even after a traumatic upper respiratory viral infection.