7% of the people in the United States (about 19 million people) suffer from chronic dysfunction of smell or taste. Anosmia is the formal name for having problems smelling.
Some of the diagnostics include: MRI, CT scans or Xrays to determine if there are any blockages in the nose. Sometimes there are a lot of polyps in the nose.
If there aren't any blockages in the nose, there is a disease process at work. There are three major parts of the taste and smell systems which can be affected by disease, the brain, the nerves and the receptors. The receptors are the mechanisms that are generally affected.
Above the mucous layer is the base olfactory epithelium which consists partially of basal cells located in the lowest cellular layer of the olfactory epithelium which are capable of mitotic cell division to form olfactory receptor neurons when functionally mature. The olfactory receptor neurons turnover approximately every 40 days and are nourished by specialized substances (proteins) secreted in saliva from your parotid gland in your mouth (for taste) and in nasal mucus from serous glands in your nose (for smell).
Although there may abnormalities in the structure of the nose, many problems in taste and smell come from biochemical factors. Protein growth factors in your saliva must be measured in an specific manner to test their function as do tests of substances in your blood and urine which can also indicate causes of your dysfunction. Vitamin and mineral deficiencies may show up: especially for Vitamin D, zinc or copper.
Treatment can be through the use of corticosteroids or keralog or through increasing the proteins secreted in nasal mucous.