Table of ContentsView AllTable of ContentsAnatomyFunctionAssociated ConditionsTests

Table of ContentsView All

View All

Table of Contents

Anatomy

Function

Associated Conditions

Tests

The olfactory epithelium is membranous tissue located inside thenasal cavity. It measures about 3 square centimeters (cm²) in adults. Containing olfactory receptor cells, it is involved in the sense of smell.

Olfactory disorders can range from a mild decrease in the ability to smell to a complete loss of smell. A loss of smell can indicate a mild illness or injury or something more serious. A decrease in the ability to smell can be an early indicator of Parkinson’s disease and Alzheimer’s disease.

Olfactory dysfunction is also associated with some psychiatric conditions, such asschizophrenia, mood disorders, andanxiety disorders, as well as some illnesses, includingCOVID-19.

Verywell / Theresa Chiechi

The olfactory epithelium is a thin, cellular tissue that runs along the roof of the nasal cavity. In adults, it is situated about 7 centimeters (cm) behind the nostrils. It is part of the nasal septum and the superior turbinatebones.

Three cell types make up the olfactory epithelium: basal, supporting, and olfactory. Olfactory receptor cells have hairlike extensions called cilia.

It used to be thought that the olfactory epithelium developed separately from the olfactory placode. More recent studies, however, have found that it develops from neural crest cells, which form in embryos.

Anatomical Variations

Another genetic disorder that can impair smell is ciliopathy. In ciliopathy, the body’s ability to make cilia is impaired. When cilia are not there or they are malformed, a person does not have the ability to smell.

The olfactory bulb is located in the front of thebrain. After the olfactory bulb receives information from the cells in the nasal cavity, it processes the information and passes it to other parts of the brain.

The loss of smell is a spectrum, with problems ranging from a change or distortion of smell (dysosmia) to a diminishment of smell (hyposmia) to the complete loss of smell (anosmia). Loss of smell is not uncommon in people withtraumatic brain injury. One study found that 15% to 35% of people with traumatic brain injury sustained a loss of smell.

Since smell and taste are so closely linked, the loss of smell often contributes to an inability to taste, making eating less enjoyable. Also, there are some dangers to not being able to smell, such as not being able to detect something burning. Lack of smell can contribute to mood disorders, too, like anxiety and depression.

Nasal cancer symptoms may include a runny nose, congestion, and a sensation of fullness or tenderness in the nose. Problems with your ability to smell can also arise. Later stages may involve nose bleeds, facial and tooth pain, and eye problems.

Early symptoms of some neurodegenerative disorders, like Parkinson’s disease and Alzheimer’s disease, include a decreased ability to smell.Some psychiatric illnesses, likeschizophrenia, mood disorders, andanxiety disorders, are also associated with olfactory dysfunction.Loss of smell is one of the key symptoms of COVID-19.

Testing for Kallmann syndrome may include blood tests to check hormone levels.Magnetic resonance imaging (MRI)of the head and nose may be done to look for anatomical abnormalities of the nose, hypothalamus, and pituitary gland. Molecular genetic testing may also be performed to identify gene mutations.

Treatment for Kallmann syndrome and nIHH usually involves hormone replacement therapy. Medication to strengthen the bones may also be used, as the absence of puberty hormones can weaken them.

Advances inDNA testing(genetic testing) using RNA sequence analysis may help diagnose ciliopathy. Ciliopathy is considered incurable, but recent advances in gene therapy could mean treatment options may be available in the future.

Your healthcare provider may order certain scans to diagnose loss of smell, likecomputed tomography (CT scan), MRI, or an X-ray. Nasal endoscopy may be used to look inside your nose. A test known as the University of Pennsylvania Smell Identification Test (UPSIT) may be done to assess the degree to which your smell is affected.

Treatment of anosmia, dysosmia, and hyposmia will depend on what is believed to be the cause of the olfactory dysfunction. Your healthcare provider may prescribe decongestants, antihistamines, or nasal sprays for allergies. If an infection is the cause, antibiotics may be in order.

Smoking is known to impair the ability to smell, so quitting smoking may also help. If there is a blockage in the nasal passage, your healthcare provider may discuss surgically removing apolypor tumor.

To definitively determine if the tumor is malignant (cancerous) or benign (noncancerous), your healthcare provider will take a biopsy of the tumor. Treatment options for nasal cancers include surgery,chemotherapy, radiation therapy, targeted therapy, andpalliative care(to ease symptoms).

5 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.SchofieldP, Moore T, Gardner A.Traumatic brain injury and olfaction: A systematic review.Front Neurol. 2014;5. doi:10.3389/fneur.2014.00005Hoffman H, Rawal S, Li C, Duffy V.New chemosensory component in the U.S. National Health and Nutrition Examination Survey (NHANES): First-year results for measured olfactory dysfunction.Reviews in Endocrine and Metabolic Disorders. 2016;17(2):221-240. doi:10.1007/s11154-016-9364-1Dibattista M, Pifferi S, Menini A, Reisert J.Alzheimer’s disease: What can we learn from the peripheral olfactory system?.Front Neurosci. 2020;14. doi:10.3389/fnins.2020.00440Borgmann-Winter K, Willard S, Sinclair D et al.Translational potential of olfactory mucosa for the study of neuropsychiatric illness.Transl Psychiatry. 2015;5(3):e527-e527. doi:10.1038/tp.2014.141Wheway G, Lord J, Baralle D.Splicing in the pathogenesis, diagnosis and treatment of ciliopathies.Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms. 2019;1862(11-12):194433. doi:10.1016/j.bbagrm.2019.194433

5 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.SchofieldP, Moore T, Gardner A.Traumatic brain injury and olfaction: A systematic review.Front Neurol. 2014;5. doi:10.3389/fneur.2014.00005Hoffman H, Rawal S, Li C, Duffy V.New chemosensory component in the U.S. National Health and Nutrition Examination Survey (NHANES): First-year results for measured olfactory dysfunction.Reviews in Endocrine and Metabolic Disorders. 2016;17(2):221-240. doi:10.1007/s11154-016-9364-1Dibattista M, Pifferi S, Menini A, Reisert J.Alzheimer’s disease: What can we learn from the peripheral olfactory system?.Front Neurosci. 2020;14. doi:10.3389/fnins.2020.00440Borgmann-Winter K, Willard S, Sinclair D et al.Translational potential of olfactory mucosa for the study of neuropsychiatric illness.Transl Psychiatry. 2015;5(3):e527-e527. doi:10.1038/tp.2014.141Wheway G, Lord J, Baralle D.Splicing in the pathogenesis, diagnosis and treatment of ciliopathies.Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms. 2019;1862(11-12):194433. doi:10.1016/j.bbagrm.2019.194433

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

SchofieldP, Moore T, Gardner A.Traumatic brain injury and olfaction: A systematic review.Front Neurol. 2014;5. doi:10.3389/fneur.2014.00005Hoffman H, Rawal S, Li C, Duffy V.New chemosensory component in the U.S. National Health and Nutrition Examination Survey (NHANES): First-year results for measured olfactory dysfunction.Reviews in Endocrine and Metabolic Disorders. 2016;17(2):221-240. doi:10.1007/s11154-016-9364-1Dibattista M, Pifferi S, Menini A, Reisert J.Alzheimer’s disease: What can we learn from the peripheral olfactory system?.Front Neurosci. 2020;14. doi:10.3389/fnins.2020.00440Borgmann-Winter K, Willard S, Sinclair D et al.Translational potential of olfactory mucosa for the study of neuropsychiatric illness.Transl Psychiatry. 2015;5(3):e527-e527. doi:10.1038/tp.2014.141Wheway G, Lord J, Baralle D.Splicing in the pathogenesis, diagnosis and treatment of ciliopathies.Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms. 2019;1862(11-12):194433. doi:10.1016/j.bbagrm.2019.194433

SchofieldP, Moore T, Gardner A.Traumatic brain injury and olfaction: A systematic review.Front Neurol. 2014;5. doi:10.3389/fneur.2014.00005

Hoffman H, Rawal S, Li C, Duffy V.New chemosensory component in the U.S. National Health and Nutrition Examination Survey (NHANES): First-year results for measured olfactory dysfunction.Reviews in Endocrine and Metabolic Disorders. 2016;17(2):221-240. doi:10.1007/s11154-016-9364-1

Dibattista M, Pifferi S, Menini A, Reisert J.Alzheimer’s disease: What can we learn from the peripheral olfactory system?.Front Neurosci. 2020;14. doi:10.3389/fnins.2020.00440

Borgmann-Winter K, Willard S, Sinclair D et al.Translational potential of olfactory mucosa for the study of neuropsychiatric illness.Transl Psychiatry. 2015;5(3):e527-e527. doi:10.1038/tp.2014.141

Wheway G, Lord J, Baralle D.Splicing in the pathogenesis, diagnosis and treatment of ciliopathies.Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms. 2019;1862(11-12):194433. doi:10.1016/j.bbagrm.2019.194433

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