Anosmia

Anosmia is the inability to detect odors. It is one type of olfactory disorder, a group of conditions that affect the sense of smell. Smell occurs when odor molecules stimulate specialized sensory cells high inside the nasal cavity. These cells send signals to the brain, where the information is interpreted as a recognizable odor. Because smell contributes significantly to flavor perception, people with anosmia often report that food tastes bland or that familiar foods and beverages no longer have their usual flavor. The basic tastes—sweet, sour, salty, bitter, and savory—may remain intact even when the sense of smell is impaired. Smell disorders can affect nutrition, quality of life, and personal safety. Identifying the underlying cause is an important first step in determining whether treatment may help.

Not every change in the sense of smell is anosmia. Understanding the type of olfactory dysfunction helps guide the evaluation.

Anosmia: Complete Loss of Smell

Anosmia refers to the inability to detect odors. It may occur during a respiratory infection, after COVID-19, because of chronic nasal or sinus disease, or following head trauma. In some cases, the cause is not immediately apparent.

Hyposmia: Reduced Sense of Smell

Hyposmia is a partial reduction in the ability to detect odors. A person may still recognize strong smells but have difficulty detecting subtle scents or distinguishing between familiar aromas.

Parosmia: Distorted Sense of Smell

Parosmia occurs when familiar odors smell different from how they normally would. Coffee, cooked food, perfume, or other everyday smells may seem unpleasant or altered. Parosmia can occur during recovery from a viral infection and may persist even when some smell function has returned.

Phantosmia: Smelling Odors That Are Not Present

Phantosmia is the perception of an odor without an identifiable external source. People may describe smelling smoke, something burnt, or another unusual odor when nothing nearby explains the sensation.These conditions have different possible causes. A clinical assessment can help distinguish between them and determine the appropriate next steps.

Loss of smell can result from a problem that prevents odors from reaching the sensory area of the nose, damage or dysfunction involving the olfactory system, or another underlying medical condition.

Viral Infections, Including COVID-19

Respiratory viruses can temporarily or persistently affect smell function. COVID-19 is a recognized cause of olfactory dysfunction, including anosmia, hyposmia, and parosmia. Some people recover their sense of smell as the infection resolves. Others experience prolonged symptoms that warrant evaluation and may benefit from olfactory training or other cause-specific management.

Chronic Sinusitis and Nasal Inflammation

Chronic rhinosinusitis can cause swelling and inflammation that interfere with airflow and the delivery of odor molecules to the olfactory region. Symptoms may include nasal congestion, thick drainage, facial pressure, and reduced smell. Treating the underlying sinus inflammation may help when it contributes to the olfactory problem. Learn more about sinusitis and its treatment.

Nasal Polyps and Structural Obstruction

Nasal polyps are noncancerous growths associated with chronic inflammation. When they obstruct airflow near the olfactory region, they can reduce the ability to smell. Other structural problems may also contribute. Depending on the findings, treatment may include medication or a surgical procedure when appropriate.

Head Trauma

Injuries to the head can damage the structures or nerve pathways involved in smell. The severity and duration of the resulting dysfunction vary, and recovery is not guaranteed. New smell loss following a significant head injury should be medically assessed, particularly when accompanied by other neurological symptoms.

Aging

Smell function may decline with age. The degree of change varies between individuals, and other causes should still be considered when smell loss is new, substantial, or progressive.

Medications, Smoking, and Chemical Exposure

Certain medications, smoking, and exposure to some chemicals or irritants can contribute to smell dysfunction. The relationship depends on the specific exposure and individual circumstances. Do not stop a prescribed medication without consulting the clinician who manages it.

Neurological and Other Medical Conditions

Smell dysfunction can sometimes occur in association with neurological disorders or other systemic conditions. Loss of smell alone does not establish a neurological diagnosis, but unexplained or progressive symptoms should be evaluated appropriately. A clinician may recommend further investigation based on the patient’s history, examination, and other symptoms.

An accurate diagnosis begins with understanding when the smell loss started, how it has changed, and whether other symptoms are present. At New York Sinus Center, an evaluation may include the following steps, depending on the patient’s needs.

Medical History

The physician may ask about:

• Whether smell loss began suddenly or gradually
• Recent viral infections, including COVID-19
• Nasal congestion, allergies, or chronic sinus symptoms
• Previous head injuries or nasal surgery
• Current medications and relevant exposures
• Changes in flavor perception or distorted smells
• The effect of symptoms on eating, nutrition, and daily life

This information helps identify possible causes and determine which examinations or tests may be useful.

Nasal Examination and Nasal Endoscopy

A nasal examination can help identify inflammation, nasal polyps, or structural abnormalities. Nasal endoscopy uses a small camera to provide a closer view of the nasal passages and the area involved in olfactory function. It may help identify conditions that are not apparent during a routine examination.

Objective Smell Testing

A standardized smell test can assess the ability to detect or identify odors. Testing may help distinguish complete loss from partial loss and provide a baseline for monitoring changes over time.

Imaging When Indicated

A CT scan may be useful when sinus disease or structural obstruction is suspected. MRI may be considered in selected cases when the clinical history or examination raises concern about the olfactory pathways or another underlying condition. Imaging is not necessary for every patient with smell loss. The decision depends on the suspected cause and the findings from the initial assessment. The goal is to establish the most likely cause of the disorder and select treatment based on the diagnosis rather than assuming that every case is related to sinusitis or a previous viral infection.

Treatment depends on the cause, duration, and severity of smell loss. Some people recover spontaneously, while others may have persistent dysfunction despite treatment.

Treating Nasal and Sinus Inflammation

When anosmia is associated with chronic rhinosinusitis, allergies, or nasal polyps, treatment may focus on reducing inflammation and improving airflow. Depending on the diagnosis, management may include saline nasal irrigation, intranasal corticosteroids, allergy-directed treatment, or other prescribed therapies. Oral corticosteroids may be appropriate in selected circumstances, but they are not suitable for everyone and require a clinician’s assessment of potential benefits and risks.

Treating Nasal Obstruction

When nasal polyps or another structural problem obstructs the olfactory region, addressing the obstruction may help restore access of odor molecules to the sensory area. Treatment may involve medication or, for selected patients with documented disease, sinus surgery. Surgery is not appropriate for every cause of smell loss and cannot guarantee recovery when the olfactory system itself has been damaged. Learn more about sinus treatment options and sinus surgery.

Olfactory Training

Olfactory training, also called smell training, is a structured rehabilitation technique that involves repeatedly smelling a set of distinct odors over an extended period. The approach is commonly considered for persistent smell loss following viral infections. It is noninvasive and may help some patients improve their olfactory function, although the degree of recovery varies.

A structured program typically involves:

• Selecting a set of recognizable odors
• Smelling each odor deliberately and repeatedly
• Practicing consistently over several months
• Monitoring changes in smell perception over time

A clinician can advise whether olfactory training is appropriate and help set realistic expectations.

Reviewing Other Contributing Factors

When the history suggests a medication effect, chemical exposure, nutritional problem, or another medical condition, treatment may involve addressing that factor or coordinating care with another specialist. The appropriate investigation depends on the clinical findings. Broad testing or supplements are not necessary for every patient.

Platelet-rich plasma (PRP) is a preparation made from a patient’s own blood that contains a concentrated amount of platelets. PRP is being investigated as a treatment for certain forms of persistent olfactory dysfunction, including smell loss following viral infections. The evidence remains developing, and PRP should not be presented as a proven treatment for every patient with anosmia. Its potential benefits, limitations, risks, and appropriate role should be discussed with a qualified clinician.

Who May be Considered for PRP?

Before considering PRP, a patient should undergo an appropriate evaluation to determine the type and possible cause of the smell disorder. This may include medical history, nasal examination, nasal endoscopy, standardized smell testing, and imaging when indicated. The physician should consider whether the loss is likely related to post-viral olfactory dysfunction or another condition that requires a different treatment approach.

What Does the PRP Evaluation Involve?

New York Sinus Center provides information about its PRP therapy program for loss of smell and taste. The practice describes an assessment that includes a review of symptoms, nasal and sinus evaluation, endoscopy, and smell testing, with imaging considered when appropriate. If PRP is being considered, the physician can explain the proposed protocol, the available evidence, potential risks, costs, and follow-up requirements. Patients should understand that improvement is not guaranteed and that treatment protocols and evidence may evolve as further research becomes available. Olfactory training may also be recommended as part of a management plan, depending on the diagnosis.

When the sense of smell is impaired, everyday safety requires additional attention because odors may no longer provide reliable warnings.

Consider the following precautions:

• Maintain functioning smoke alarms and install appropriate gas and carbon monoxide detectors.
• Check food expiration dates and storage times rather than relying on smell to judge freshness.
• Follow safe food-handling practices and discard food when its safety is uncertain.
• Use timers when cooking and remain attentive to appliances.
• Be cautious when handling household chemicals and follow their safety instructions.
• Monitor appetite, weight, and nutrition if food seems less appealing.

If smell loss affects eating or causes unintentional weight changes, discuss this with a healthcare professional. Persistent changes in smell can affect nutrition and quality of life as well as safety.