Version May 2024
INTRODUCTION — The 2016 United States National Health and Nutrition Examination Survey (NHANES) demonstrated that 12.4 percent of United States adults aged ≥40 years had some degree of olfactory dysfunction, with 3.2 percent having anosmia (complete loss of smell) or severe hyposmia (decreased sense of smell) [1]. Many individuals with olfactory disorders report a decreased quality of life, particularly those with severe olfactory dysfunction [2]. Olfaction plays a significant role in our detection of the aroma and flavor of foods and in the awareness of fragrances in our environment. Disruption of the experience of a pleasant sensory exposure can sometimes cause depression. Patients may no longer look forward to eating and drinking, and they often refuse to go out to dinner and associate with friends. Important nutritional deficiencies can lead to marked weight loss [3]. Additional dangers associated with olfactory impairment include the inability to detect the odors of spoiled food, smoke, and leaking gas. Furthermore, the importance of olfaction cannot be overemphasized to certain professions such as chefs, perfumers, and fire fighters [4]. Some individuals with olfactory disorders find it difficult to function in everyday life [5].
The evaluation of patients with abnormalities of taste or olfaction requires a multidisciplinary evaluation. The approach to these patients is reviewed here. The anatomy of taste and olfaction and the causes of dysfunction in these areas are discussed separately. (See "Taste and olfactory disorders in adults: Anatomy and etiology".)
DEFINITIONS — Normogeusia and normosmia describe normal taste and smell functions, respectively. Definitions of abnormalities of taste and olfaction include:
●Abnormalities of taste function
•Hypogeusia – Diminished taste function to one or more specific tastants
•Ageusia – Absent taste function
•Dysgeusia – Altered (sweet, sour, salty, bitter, or metallic) perception of taste in response to a tastant stimulus
•Aliageusia – Taste disturbance in which a typically pleasant-tasting food or drink tastes unpleasant
•Phantogeusia – Unpleasant taste due to a gustatory hallucination (in the absence of any stimulus)
●Abnormalities of olfaction
•Hyposmia – Diminished smell function (also sometimes referred to as microsmia)
•Anosmia – Absent smell function
•Parosmia – Abhorrent odor perception either with an odorant stimulus (troposmia or smell distortion) or without an odorant stimulus (phantosmia)
•Dysosmia – A general term describing distortion of smell sensations
EVALUATION
Clinical history — Many patients may not recognize or spontaneously mention olfactory impairment [6]; between 54 to 74 percent of older adults with measurable smell loss do not recognize the deficit [1,7]. The sensitivity of self-reporting can be improved by asking more detailed questions [8] such as the following survey questions [1]:
●“During the past 12 months, have you had a problem with your ability to smell, such as not being able to smell things or things not smelling the way they are supposed to?”
●“How would you rate your ability to smell now compared with when you were 25 years old? Is it better now, worse now, or is there no change?” (This can be adjusted based upon the patient’s age.)
●“Do you sometimes smell an unpleasant, bad, or burning odor when nothing is there?”
A positive response to any of these questions can signify a possible olfactory impairment [6].
For any patient who reports a change in their sense of smell or taste, several features in the clinical history can provide clues to the etiology, including the timing of symptom onset (ie, sudden versus gradual), precipitating events, associated symptoms, and possible environmental exposures (table 1 and table 2). As examples:
●Sudden loss of olfaction can occur following a head injury [9].
●Sudden loss of taste or smell can occur in the setting of a current or recent viral upper respiratory infection [10]. In particular, sudden anosmia and ageusia have been reported as presenting symptoms in some patients with coronavirus disease 2019 (COVID-19) [11-14] (see "COVID-19: Clinical features", section on 'Initial presentation'). Conversely, allergic rhinitis, nasal polyps, or neoplasms of the nasopharynx are associated with more gradual onset of hyposmia or anosmia [15]. Intermittent olfactory impairment may also be seen in allergic rhinitis.
●Associated symptoms such as headache, behavior disturbances, or neuromuscular abnormalities may indicate a central nervous system problem [16].
●Occupational exposures (chemicals, toxic fumes), tobacco and alcohol use, and medications may be associated with alterations in taste and smell, and such exposures should be evaluated (table 3 and table 4) [17,18]. (See "Taste and olfactory disorders in adults: Anatomy and etiology", section on 'Etiologies of taste and olfactory dysfunction'.)
Physical examination — Even in patients with a history of head trauma, a physical examination is necessary to fully evaluate the cause of olfactory and taste dysfunction.
●Nasal and sinus examination – Nasal and paranasal sinus diseases are the most common causes of olfactory abnormalities, and a thorough examination of the nasal cavity and paranasal sinuses is essential. This is typically not possible in the primary care setting; thus, a referral to an otorhinologist is appropriate for a complete evaluation.
●Oral examination – A thorough examination of the oral cavity should be performed, including evaluation without dental prostheses in place (if present) for periodontal disease, intraoral lesions, and the distribution of taste papillae. Many oral conditions such as fungal infections [19] and glossitis [20] are associated with taste dysfunction.
●Neurologic examination – A focused neurologic examination, with particular attention to cranial nerve function, should be performed, as olfactory complaints are occasionally the first symptoms of a neurologic problem [16].
DIAGNOSTIC TESTING — Subjective complaints of taste or olfactory loss require objective confirmation before embarking on a more extensive evaluation, particularly because many individuals confuse the ability to perceive "taste" and "flavor." Taste is related to the ability to detect sweet, sour, salty, and bitter, and flavor involves the combined features of smell, taste, irritation, texture, and temperature. The smell, or aroma, of food and beverages is the most important contributor to flavor; as a result, derangement of smell is often described by patients as a problem with taste. (See "Taste and olfactory disorders in adults: Anatomy and etiology", section on 'Flavor perception is multisensory'.)
A variety of tests, including objective assessments of smell and taste, and tests such as imaging and laboratory studies, are performed on patients with olfactory or taste dysfunction.
Standardized olfactory tests — Although primary care clinicians do not typically conduct olfactory or taste testing in their offices, superficial testing using odorants such as chocolate, turpentine, coffee, moth balls, or soap may be used to test odor sensitivity. Standardized olfactory tests may be more helpful in determining the degree of olfactory impairment. Such tests that can be administered in a primary care office include:
●The University of Pennsylvania Smell Identification Test (UPSIT). The test involves 40 micro-encapsulated odorants that are released by rubbing with the tip of a pencil; identification of the odor is made from among four choices.
●"Sniffin’ sticks" (or Threshold, Discrimination, Identification Test [TDIT]). The test can be administered in a primary care office and may take as little as four minutes [21]. Sniffin’ sticks (Burghart Sniffin’ Sticks) can be purchased commercially from select vendors.
Referral to a local otolaryngologist or a smell center, where more detailed testing can be easily and efficiently performed, is indicated when significant impairment is identified on any of these office-based tests. A list of smell centers can be found at the Anosmia Awareness; additional smell centers are available at many academic medical centers.
Chemosensory testing — A number of quantitative psychophysical tests are used to evaluate chemosensation. These are threshold tests which determine the minimum concentration that can be detected by the patient. In addition, the ability to discriminate and identify different taste and smells is also assessed. At the beginning of testing, the patient is interviewed by a taste and smell technician. The details of the taste and olfactory complaints are noted, including the date of onset, the degree of impairment, and any circumstances that occurred at the onset of the difficulty. As an example, a history of viral infection preceding the problem would be noted.
●Butanol threshold test – The butanol threshold test evaluates olfactory function [22]. This test uses N-butyl alcohol, a sweet-smelling substance, as the odorant. The patient is presented with bottles containing either water or odorant in an aqueous concentration series ranging from 2 x 10(-7) to 4 percent. Each nostril is tested separately. The point of transition between detection and no detection is determined and the threshold concentration is converted into a numeric score. Appropriate tests are included to identify possible malingering.
An odor identification and trigeminal function test also are administered [22]. Eight different odorants are presented to each nostril and the patient is asked whether they are aware of a sensation from the odorant and if it can be specifically identified. Odorants that are irritating are used to assess trigeminal function in the nasal mucosa.
●Whole-mouth taste test – Whole-mouth taste testing assesses the patient's ability to detect, identify, and rate the intensity of various concentrations of sweet, sour, salty, and bitter taste solutions [23]. The patient's data are compared with data obtained from "normal" control subjects and are assigned to a percentile score/rank (number of subjects whose responses are below those of the patient) for each taste quality.
●Spatial test – Spatial testing is performed since localized losses of taste often go unnoticed. Function in the different taste bud fields is assessed separately with regional testing [23]. At our taste center, a cotton swab soaked in a specific taste solution is separately applied to four quadrants of the tongue and to each half of the soft palate. Taste function in the throat is assessed by asking the patient to swallow a portion of each taste solution. All of the regions mentioned are independently tested with each taste solution; in each case, the patient is asked to identify the taste quality and estimate its intensity.
●Flavor discrimination test – The flavor discrimination test is used to evaluate the combination of both taste and olfactory sensation. Four different stimulant solutions are made available which differ in the amount of sweetener present. These are presented in a random order and the patient is asked to taste the various solutions [24].
Somatosensory testing — Evaluation of somatosensation in the mouth is carried out by the use of Semmes-Weinstein monofilaments [25]. A patient's contact detection (pressure) threshold is determined by applying a monofilament which exerts a force when applied to a peripheral nerve field proportional to the gauge of the monofilament. Various areas in the interior of the mouth are tested; reduced sensation to pressure suggests abnormalities of one (or more) cranial nerves, depending upon the specific region affected [26]. (See "Taste and olfactory disorders in adults: Anatomy and etiology", section on 'Taste'.)
Imaging — The decision to obtain imaging in the evaluation of a patient with taste or olfactory dysfunction depends upon concerns for potential etiologies raised from the history and physical examination.
In any patient with a history of head trauma, neurologic abnormalities on physical examination, or in whom there is a concern for neoplasm, we obtain magnetic resonance imaging (MRI) of the head with contrast. For patients in whom sinus disease is suspected, computed tomography (CT) of the sinuses is preferred; it is also useful for studying the skull base. MRI can also evaluate the sinuses, but it is not the modality of choice for this area.
In patients with idiopathic olfactory loss and none of the above features, we typically do not order imaging as it is often unrevealing. In one retrospective cohort study of 839 patients with olfactory loss in which MRI was used to evaluate idiopathic olfactory loss in 55 percent of patients, only 0.8 percent of patients were found to have an imaging abnormality that explained their olfactory loss [27].
Laboratory studies — For patients in whom the etiology of taste or olfactory dysfunction is certain based upon the clinical history and physical examination, laboratory evaluation is typically not needed. However, in those patients for whom the cause is only suspected or is unknown, blood tests might be useful (table 1 and table 2).
For such patients, we obtain a complete blood count, sedimentation rate (or C-reactive protein), tests of kidney and liver function, antinuclear antibodies, and a thyroid profile as part of the initial evaluation.
For those with symptoms suggestive of Sjögren's syndrome, detection of antibodies to Ro/SSA and LA/SSB may be helpful in identifying the cause.
Measurement of lead, arsenic, and other heavy metal concentrations may be warranted in selected patients with dysgeusia, depending upon risk factors for exposure (eg, occupation, region of residence, well water use).
For patients with glossitis or other features of B12 deficiency, a vitamin B12 level should be checked.
Zinc levels should be measured in patients with suspected malnutrition.
Other testing — For patients with suspected allergic rhinitis, the allergist plays an important role in the diagnosis; evaluation of sensitivity to features in the home and work environment is essential. Skin testing may be necessary to confirm sensitivity to specific antigens.
TREATMENT — The treatment of a taste and olfactory disorder typically depends upon the etiology.
Olfactory dysfunction — The treatment of olfactory dysfunction generally depends upon the etiology, although some therapies, such as smell, or olfactory, training and intranasal glucocorticoids, may be effective for olfactory loss of a variety of etiologies.
Nasal and paranasal sinus disease — Nasal and paranasal sinus diseases are the most common causes of olfactory abnormalities, and treatment of the underlying disease will typically improve olfactory dysfunction. Obstructive disorders such as allergic rhinitis, nonallergic rhinitis, rhinosinusitis, and nasal polyposis require relief of the obstruction and treatment of an accompanying infection, if present. Some patients with nasal and paranasal sinus disease and olfactory loss, however, do not have significant obstruction on endoscopy or computed tomography (CT) studies. It is possible that such patients have damage to olfactory receptors resulting from products of inflammation [28].
For patients with nasal and paranasal sinus disease and olfactory loss, olfactory training may be a useful adjunct to medical therapy. Although there are few high-quality data to support its efficacy in this patient population, there are no harms associated with such treatment, and olfactory training may improve olfactory function. We typically add olfactory training to medical therapy for patients with more severe olfactory dysfunction and those with symptoms that persist despite appropriate treatment of the underlying sinonasal disease. (See 'Postviral olfactory dysfunction' below.)
●Chronic rhinosinusitis (with or without nasal polyposis)
•Medical therapy – Systemic glucocorticoids reduce mucosal edema and polypoid elements, effectively treating the majority of nasal and paranasal sinus diseases and associated symptoms, including olfactory dysfunction. However, long-term use can cause a variety of adverse effects (see "Major adverse effects of systemic glucocorticoids"). Thus, these drugs are best employed in short courses of two to three weeks [29]. Recurrent symptoms may occur after cessation of therapy but often can be prevented by adding supportive long-term treatment such as intranasal glucocorticoids.
There are a variety of intranasal glucocorticoid preparations that can be administered topically via spray, squirt, or irrigation. Inadequate drug dispersal can limit the efficacy these preparations. An applicator that produces a squirt rather than a spray may be used to deliver the drug higher up in the nasal cavity to reach the localized area of olfactory mucosa [30].
Steroid irrigations can be used to achieve better dispersal of the medication within the nasal cavity. Budesonide irrigations, proven safe for long-term use [31], can be used concentrated (0.5 mg/2 mL ampule) or diluted in saline to achieve a greater volume irrigant. In a study evaluating patients with severe nasal polyposis and asthma, the use of budesonide nasal irrigations following a course of systemic glucocorticoids improved nasal symptoms, including olfactory dysfunction, compared with systemic glucocorticoids alone [32].
A coexisting bacterial sinus infection may limit the effectiveness of intranasal glucocorticoids; two to three weeks of appropriate antibiotic treatment may be helpful in such circumstances. (See "Microbiology and antibiotic management of chronic rhinosinusitis", section on 'Antimicrobial therapy'.)
The treatment of nasal and paranasal sinus disease with corticosteroids is reviewed in detail elsewhere. (See "Chronic rhinosinusitis without nasal polyposis: Management and prognosis", section on 'Saline'.)
•Surgery – Although surgical intervention may be necessary if medical therapy is ineffective in the management of chronic rhinosinusitis, the success of surgery in addressing olfactory dysfunction is variable [33]. (See "Chronic rhinosinusitis without nasal polyposis: Management and prognosis" and "Chronic rhinosinusitis with nasal polyposis: Management and prognosis".)
-In one series including patients with nasal polyposis, anosmia improved in 52 percent of patients treated with endoscopic sinus surgery [34]. Greater disease severity, determined by the Kennedy sinus disease staging system, was associated with greater olfactory loss and persistent anosmia. Postoperative endoscopic examination revealed normal mucosa in 92 percent of patients whose sense of smell improved, compared with 17 percent of patients with persistent anosmia.
-By contrast, a multiinstitutional prospective cohort study found that patients with severe olfactory dysfunction showed significant improvement in olfaction after endoscopic sinus surgery, while patients with milder impairments in olfaction did not significantly improve [35]. The presence of nasal polyposis correlated with surgical success.
Patients may need to continue medical management (nasal steroids, antihistamines, and leukotriene inhibitors) in the postoperative period to limit mucosal inflammation [36].
●Allergic rhinitis – Treatment of allergic rhinitis includes allergen avoidance, systemic or intranasal antihistamines, and intranasal glucocorticoids. Desensitization is necessary in some cases. Leukotriene inhibitors can reduce the size of nasal polyps and improve olfaction in some patients with polyps and anosmia/hyposmia [37], although these agents are no longer preferred for the treatment of allergic rhinitis (see "Pharmacotherapy of allergic rhinitis", section on 'Overview of treatment'). Treatment of chronic sinusitis and nasal polyposis, however, has variable effectiveness for improving anosmia in patients with allergic rhinitis as the underlying etiology.
Postviral olfactory dysfunction — For all patients with postviral olfactory dysfunction (PVOD), we suggest smell, or olfactory, training, as this can improve the recovery of olfactory function in patients with persistent symptoms.
Olfactory training typically involves deeply sniffing at least four different odors for 10 seconds twice daily for at least 12 weeks. The odorants used are distinct and strong and typically include flowery (eg, rose), fruity (eg, lemon), aromatic (eg, clove), and resinous (eg, eucalyptus). Other odorants such as cinnamon, vanilla, orange, and banana have been used. Patients may perform olfactory training at home on their own; preassembled “smell training kits” may be purchased, or vials of essential oils can be used for this purpose.
●In a 2020 meta-analysis including four studies (two randomized controlled trials and two prospective cohort studies), 286 patients with PVOD received olfactory training of varying duration and treatment protocols, lasting from four to nine months [38]. Olfactory training was associated with an increased chance of clinically important olfactory improvement (OR 2.77, 95% CI 1.67-4.58) compared with not receiving such therapy.
●In a 2020 systemic review, olfactory training was effective in improving olfactory function in PVOD [39]. In all 10 studies reviewed, olfactory training was found to improve olfactory function; higher concentrations of odorants, higher molecular weight odorants, longer duration of training (up to 52 weeks), and an increased variety of odors used were all found to be most beneficial in improving olfactory function.
The proposed mechanism of action is that, with repeated olfactory stimulation, olfactory training can promote olfactory neuron regeneration or the creation of new synaptic connections [40-42].
For some patients with persistent, severe PVOD, the addition of budesonide nasal irrigations to olfactory training may further improve olfactory outcomes, although data are limited on this subset of patients.
Olfactory dysfunction of various causes — Many studies of the treatment of olfactory dysfunction include patients with olfactory loss of different causes, thus making the determination of efficacy for a specific etiology difficult. However, olfactory training appears to have efficacy in the treatment of olfactory loss of a variety of causes. As examples:
●In a study of patients with olfactory loss, excluding patients with sinonasal disease, olfactory training improved olfactory function in about 30 percent of subjects [43]. In another study of patients including patients with chronic idiopathic olfactory loss, olfactory training was shown to induce changes on functional magnetic resonance imaging (MRI) in olfactory regions [40].
●In a randomized controlled trial including patients with olfactory loss, excluding patients with sinonasal disease, budesonide nasal irrigations used in combination with olfactory training improved outcomes in patients with olfactory loss compared with olfactory training alone [44].
●In a study including older adults with presumed aging-related olfactory dysfunction, 20 percent of patients who underwent olfactory training for a longer (five-month) period showed significant improvement in smell sensitivity and smell discrimination after training, although odor identification ability did not improve [45]. The training also resulted in improved general mood and a reduction in depression symptoms.
●In a study including patients with Parkinson disease and olfactory dysfunction, olfactory training improved olfactory function [46].
Other disorders
Parosmia — Parosmia or phantosmia (a phantom, unpleasant odor perception) is common in adults (6 percent of adults over age 40 years in one large study) [47]. Parosmia is associated with prior head trauma, the presence of persistent dry mouth, nasal congestion, and self-reported general poor health status and is more prevalent in females than males (table 2). Symptoms frequently resolve with successful treatment of underlying conditions, such as dry mouth or nasal congestion. However, symptoms may persist despite appropriate treatment. In case reports of patients with phantosmia, antiseizure medications (ie, phenytoin and valproic acid), and antimigraine medications (ie, topiramate and verapamil) have shown some positive results in some patients, particularly in those with olfactory disturbance due to migraine [48,49]. However, these are generally not widely used. For patients with persistent, disabling parosmia despite appropriate treatment of any underlying condition, treatment with clonazepam (0.5 to 1 mg orally given once daily in the evening) is another treatment option, as we have used this in several patients with some success.
Surgical excision of olfactory mucosa is another treatment option but should only be considered for patients with persistent, disabling symptoms resistant to medical therapy [49]. Ultimately, however, there is an overall lack of data regarding management and there is no uniformly accepted treatment for this disorder.
Dysgeusia — The treatment of dysgeusia can be challenging. Treatment of the underlying condition or conditions causing the dysgeusia often alleviates the problem (table 1). For example, if gastroesophageal reflux is a significant etiologic factor, medications to reduce acid such as histamine 2 (H2) receptor antagonists and proton pump inhibitors (PPIs) can be helpful. However, there are many instances where the complaint persists despite appropriate treatment of the underlying condition, and for patients in whom the condition is idiopathic, no directed treatment can be offered.
For patients with persistent, intolerable dysgeusia despite treatment of an identifiable underlying cause, we suggest treatment with clonazepam (0.5 to 1 mg orally given once daily in the evening). Based upon indirect evidence from patients with burning mouth syndrome and dysgeusia [50], dysgeusia related to cancer treatment [51], as well as our own successful clinical experience treating idiopathic dysgeusia, clonazepam treatment is often beneficial in improving symptoms. Clonazepam causes brainstem serotonergic descending inhibition, binding more to central than peripheral benzodiazepine receptors [52]. It has a long half-life and is generally well tolerated [53].
TREATMENTS WE DO NOT RECOMMEND
Olfactory dysfunction — There are a variety of treatments that have been studied for the treatment of olfactory dysfunction, although there is a lack of high-quality evidence supporting their efficacy. Theophylline, systemic and intranasal, has been used to treat patients with olfactory loss with some success, although high-quality evidence supporting its efficacy is limited [54]. As an example, in an open-label, noncontrolled, prospective study of 312 patients with hyposmia from a variety of causes (31 percent postinfectious, 31 percent allergic rhinitis, 14 percent post-head trauma), theophylline (200 to 800 mg) was found to improve subjective olfactory loss in 50 percent, with higher doses associated with improved olfactory function [55]. Improvement persisted as long as treatment was continued, which extended from 6 to 72 months. However, high-quality data, including randomized controlled trials, are needed for further evaluation of efficacy.
Intranasal sodium citrate spray has also been shown to improve olfactory function in some patients with olfactory loss [56,57], although this treatment is not widely used and additional trials are needed to evaluate efficacy.
PROGNOSIS — The prognosis for recovery of olfactory and taste dysfunction is variable, and generally depends upon the etiology.
Postviral olfactory dysfunction (PVOD) will typically improve over time [58], although symptoms may persist in some patients, even with olfactory training. Olfactory and taste impairment resulting from head trauma are less likely to resolve, although in some cases rapid improvement may occur with resolution of edema and hemorrhage. Olfactory neurons have regenerative capabilities, and, in cases of neural damage, improvement may occur over a period of days or even years [59,60].
In a longitudinal study of 542 patients with olfactory loss of various etiologies, improvement in olfactory function occurred in 57 percent of anosmic and 43 percent of microsmic patients over time (3 months to 24 years); complete recovery was seen in 11 and 23 percent of patients with anosmia and microsmia (hyposmia), respectively [61]. Recovery was related to patient age, severity of initial loss, and duration of loss at first testing; etiology of olfactory loss, sex, and smoking did not predict recovery.
SUMMARY AND RECOMMENDATIONS
●Importance of clinical history – For any patient who reports a change in their sense of smell or taste, several features in the clinical history can provide clues to the etiology, including the timing of symptom onset (ie, sudden versus gradual), precipitating events, associated symptoms, and possible environmental exposures (table 1 and table 2). (See 'Clinical history' above.)
●Thorough examination of the nasal cavity and paranasal sinuses – Nasal and paranasal sinus diseases are the most common causes of olfactory abnormalities, and a thorough examination of the nasal cavity and paranasal sinuses is essential. This is typically not possible in the primary care setting; thus, a referral to an otorhinologist is appropriate for a complete evaluation. A focused neurologic examination and a careful examination of the oral cavity should also be performed. (See 'Physical examination' above.)
●Confirm subjective complaints with objective testing – Subjective complaints of taste or olfactory loss require objective confirmation before embarking on a more extensive evaluation. Although primary care clinicians do not typically conduct olfactory or taste testing in their offices, superficial testing using odorants such as chocolate, turpentine, coffee, moth balls, or soap may be used to test odor sensitivity. Standardized olfactory tests may be more helpful in determining the degree of olfactory impairment. Such tests that can be administered in a primary care office include the University of Pennsylvania Smell Identification Test (UPSIT) and Threshold, Discrimination, Identification Test [TDIT] using “Sniffin’ sticks.” (See 'Standardized olfactory tests' above.)
●Imaging in select patients – In any patient with a history of head trauma or neurologic abnormalities on physical examination, or in whom there is a concern for neoplasm, we obtain magnetic resonance imaging (MRI) of the head with contrast. For patients in whom sinus disease is suspected, computed tomography (CT) of the sinuses is preferred. In patients with idiopathic olfactory loss and none of the above features, we do typically do not order imaging as it is often unrevealing. (See 'Imaging' above.)
●Treatment directed at underlying cause of olfactory dysfunction – The treatment of olfactory dysfunction generally depends upon the etiology, although some therapies, such as smell (olfactory) training and intranasal glucocorticoids, may be effective for olfactory loss of a variety of etiologies.(See 'Treatment' above.)
Nasal and paranasal sinus diseases are the most common causes of olfactory abnormalities. Obstructive disorders such as allergic rhinitis, nonallergic rhinitis, rhinosinusitis, and nasal polyposis require relief of the obstruction and treatment of an accompanying infection, if present. Some patients with nasal and paranasal sinus disease and olfactory loss, however, do not have significant obstruction, although improvement often occurs with treatment of the underlying nasal sinus disease. Smell or olfactory training may be a useful adjunct to medical therapy, particularly for patients with more severe olfactory dysfunction and those with symptoms that persist despite appropriate treatment of the underlying sinonasal disease. (See 'Nasal and paranasal sinus disease' above.)
●Olfactory training for postviral olfactory dysfunction – For patients with postviral olfactory dysfunction (PVOD), we suggest smell, or olfactory, training, as this can improve the recovery of olfactory function (Grade 2C). (See 'Postviral olfactory dysfunction' above.)
●Treatment directed at underlying cause of dysgeusia – The management of dysgeusia can be challenging, although treatment of the underlying condition or conditions often alleviates the problem. For patients with persistent, intolerable dysgeusia despite treatment of an identifiable underlying cause, we suggest treatment with clonazepam (0.5 to 1 mg orally given once daily in the evening) (Grade 2C). Based upon indirect evidence from patients with burning mouth syndrome and dysgeusia, dysgeusia related to cancer treatment, as well as our own successful clinical experience treating idiopathic dysgeusia, clonazepam treatment is often beneficial in improving symptoms and is well tolerated.
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Norman Mann, MD, who contributed to an earlier version of this topic review.
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