January 2012

Loss of Saliva and Nasal Mucus Inhibits Taste and Smell Function

Saliva and nasal serous deliver growth factors to taste buds and olfactory epithelial cells. If, for any reason, saliva and nasal mucus secretions are diminished then the function of taste buds and olfactory epithelial cells also diminishes. In this manner, growth factors present in saliva or nasal mucus cannot be delivered to taste buds and olfactory epithelial cells and loss of taste and smell function occur.

Taste and smell are sensory systems dependent upon receptors, nerves and brain to maintain normal function. Taste and smell are chemical senses whose receptors depend upon growth factors to maintain them. Any systemic or local changes which inhibit growth factor secretion causes taste and smell loss and eventually, with contributions from nerves and brain, taste and smell distortions. Any systemic or local change which inhibits saliva or nasal mucus also causes taste and smell loss and eventually taste and smell distortions.

There are multiple pathologies which cause saliva and nasal mucus loss and thereby inhibit growth factor delivery to taste buds and olfactory epithelial cells.

X-irradiation to the head or neck inhibits saliva and nasal mucus secretion and thereby cause taste and smell dysfunction. Irradiation of this type occurs in about 50,000 patients yearly primarily to treat cancers of the head and neck. Secretion inhibition can be transient and return a few months after irradiation ends or it can be permanent such that xerostomia (dry mouth) or xerorhinorrhea (dry nose) occurs. Only with return of these secretions can delivery of growth factors present in saliva and nasal mucus restore and correct taste and smell dysfunction. There is little known treatment to restore these glandular secretions after irradiation. However, over time secretions can and do return spontaneously in many patients.

Autoimmune disorders can cause xerostomia and xerorhinorrhea. These disorders include scleroderma, sarcoidosis, systemic lupus erythematosus, Sjogren’s syndrome and many others. In these disorders lymphocytes and other chronic inflammatory cells infiltrate the salivary and nasal serous glands replacing these secreting glands with fibrotic changes which cause xerostomia and xerorhinorrhea. These changes occur in each of these disorders but severity varies a great deal. Treatment of the underlying autoimmune pathology which initiated these diseases can not only correct the underlying pathology but also can induce saliva and nasal mucus secretion thereby correcting the taste and smell dysfunction.

Many other diseases and pathological processes inhibit saliva and nasal mucus secretions. Hormone dysfunctions such as diabetes mellitus and hypothyroidism, hypertension, infectious processes (bacterial, viral, fungal), cystic fibrosis and drug treatments of various sorts (diuretics, anticholinergics, antidepressants, anxiolytics) have been reported to inhibit these glandular secretions. Ageing has also been reported associated with diminished glandular secretions and sensory dysfunction. These processes affect many thousands of patients in the United States. Treatment to correct these changes are specific for the causative process.

Many publications in the medical literature have dealt with this issue.

References

1. Henkin RI, Talal N, Larson AL, Mattern CF. Abnormalities of taste and smell in Sjogren’s syndrome. Ann Intern Med. 1972;76:375-383.

2. Powell RD, Larson AL, Henkin RI. Nasal mucous membrane biopsy in Sjogren’s syndrome: a new diagnostic technique. Ann Intern Med. 1974;81:25-31.

3. Mossman KL, Henkin RI. Radiation induced changes in taste acuity in cancer patients. Int J Radiat Oncol Biol Phys. 1978;4:663-670.

4. Mossman KL, Chencharick JD, Scheer AC, Walker WP, Ornitz RD, Rogers CC, Henkin RI. Radiation-induced changes in gustatory function: comparison of effects of neutron and photon irradiation. Int J Radiat Oncol Biol Phys. 1979;5:521-528.