REVIEW NORMAN M. MANN, MD Assistant Professor of Medicine, Director, Smell and Taste Clinic, University of Connecticut Health Center, Farmington Management of smell and taste problems ■ ABSTRACT HE LOSS OF SMELL or taste too often does T not get the medical attention it deserves. Lost or impaired smell or taste should be taken seriously, as This is unfortunate because of the serious it puts a person at higher risk for toxic exposures, such as implications for the patient’s well-being. gas leaks, smoke, and rotting food, and it also takes away In many patients, smell or taste problems the enjoyment of some of life’s pleasures, such as the follow a viral upper respiratory tract infection, fragrance of flowers or the taste of good food or fine wine. which can damage sensory cells. These In many patients, the loss follows a viral upper respiratory patients need to be told that the damaged cells tract infection, and the only real treatment is to reassure may regenerate with time, resulting in the patients that the problem may resolve if the damaged return of smell and taste sensation. In other sensory cells regenerate. In other patients, the loss has patients, the loss has more subtle causes and requires a more in-depth workup. This article more subtle causes and deserves a careful investigation presents an approach to all patients with and appropriate treatment. This article reviews the proper impaired smell or taste. steps to take when investigating and treating chemosensory difficulties. ■ THE RISKS ■ KEY POINTS Loss or impairment of smell or taste puts people at greater risk of toxic exposures. With the loss Aside from increasing the risk of toxic exposures, the loss of of smell, they may be unable to detect leaking smell and taste often leads to depression, anorexia, and gas, smoke, or the odor of rotting food. weight loss. Interestingly, 80% of the patients seen in our smell and taste clinic have not been told by A thorough workup includes smell and taste testing, their physician to get a gas detector in the imaging studies, and blood testing. home. With the loss of smell and taste, many Gastric reflux is a common cause of taste dysfunction. pleasurable life experiences disappear, such as the fragrance of perfume or flowers or the taste of good food or fine wine, and this puts the individual at higher risk for depression, anorexia, and weight loss. According to one estimate,1,2 more than 2 million adult Americans have some type of chemosensory disorder. ■ CAUSES OF SMELL DYSFUNCTION Organs of smell sensation The sense of smell involves the passage of odor-stimulant molecules through the nasal CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 69 • NUMBER 4 APRIL 2002 329 SMELL AND TASTE PROBLEMS MANN canal, where they interact with olfactory cells University of Pennsylvania, it has been report- in the nasal epithelium. Messages are then ed as the cause in 17.6% of cases.4 It has been sent via the olfactory (first cranial) nerves stated that 5% to 30% of patients with head through the cribriform plate of the ethmoid injury have some olfactory loss.5 This may be bone to the olfactory bulb in the brain, locat- due to blockage of the nasal canal, but the ed just above the nose. Thereafter, informa- most common cause is injury to the delicate tion is transmitted to different portions of the olfactory nerves as they travel from the nasal brain. Olfactory cells are thought to regener- canal through the cribriform plate to the ate every 30 or 60 days.3 olfactory bulb. Even mild jarring injuries can cause disruption of the neural pathways. Types of smell impairment Damage to the bulb itself and other central Normosmia is the name given to normal areas can also occur. smell. Smell dysfunction can have various pre- sentations: Nasal polyps, tumors • Hyposmia, diminished sense of smell Nasal polyps and tumors in the nasal canal • Parosmia, aberrant odor perception, either can impede the progress of odorants. Polyps without an odor stimulus (phantosmia) or are common. The incidence of polyps as a with an odor stimulus (distortion) cause of smell impairment varies in reports • Anosmia, total loss of smell. from 41% to 69%.6 People who have lost their sense of smell sometimes retain their ability to detect pun- Endocrine conditions gent odors such as ammonia; however, this is Endocrine disturbances such as diabetes mel- due to stimulation of the trigeminal (fifth cra- litus,7 hypothyroidism, and hypogonadism nial) nerve endings, which cover the oral cav- (eg, Turner syndrome, Kallmann syndrome)8 ity as well as the nose. are occasionally associated with olfactory Loss of smell can be the result of either impairment. Kallmann syndrome is charac- mechanical obstruction of or neurologic dam- terized by hypogonadotropic hypogonadism 25% of patients age to the nasal cavity, the neuroepithelium in with agenesis of the olfactory bulbs. Adrenal with smell loss the nasal canal, or the central olfactory ele- insufficiency9 and pseudohypoparathyroid- ments. In some patients, odorants are blocked ism10 may also present with olfactory dys- had a recent from reaching olfactory receptors, while in function. viral respiratory others peripheral olfactory receptors, nerve conduction pathways, or central olfactory Aging infection areas are damaged. A loss of olfactory sensitivity occurs with age. Degenerative changes occur in receptors in Rhinitis the nasal canal and even the olfactory bulb. At our clinic, mechanical obstruction is most The neurotransmitter pathways can also be commonly due to rhinosinusitis (25% of affected. According to some estimates, almost cases). Allergic and nonallergic rhinitis are everyone has some type of smell impairment significant causes of obstruction. by age 60 or 70, and half of those in their 80s are anosmic.11 Viral infection From 14% to 25% of patients who report par- Environmental toxins tial or total impairment of smell have had a Environmental toxins can cause severe distur- recent viral upper respiratory tract infection. bance in the olfactory system. They can enter Viral infection is thought to damage peripher- through the blood stream or inspired air. al olfactory receptors and neural pathways to Injury can involve the neuroepithelium or the the brain. olfactory nerves or both, and it can be reversible or irreversible. For example, expo- Head trauma sure to arsenic, benzene, carbon disulfide,12 At our clinic, head trauma has been the cause cadmium, sulfur dioxide, chlorine, chromium of olfactory impairment in 11% of cases; at the fumes, and cigarette smoke13 can produce 330 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 69 • NUMBER 4 APRIL 2002 T ABLE 1 Drugs that can cause impaired smell or taste Antidepressants and anticonvulsants Amitriptyline, carbamazepine, clomipramine, clozapine, desipramine, doxepin, fluoxetine, imipramine, lithium, phenytoin, trifluoperazine Antihistamines and cold medications Chlorpheniramine, loratadine, pseudoephedrine, terfenadine Antihypertensives and cardiac medications Acetazolamide, adenosine, amiloride, benazepril and hydrochlorothiazide, betaxolol, captopril, clonidine, diltiazem, enalapril, ethacrynic acid, nifedipine, propranolol, spironolactone Anti-inflammatories Auranofin, colchicine, dexamethasone, diclofenac, dimethyl sulfoxide, gold, hydrocortisone, d-penicil- lamine, penicillamine Antimicrobials Ampicillin, ciprofloxacin, clarithromycin, ofloxacin, streptomycin, tetracyclines Antineoplastics Cisplatin, doxorubicin, methotrexate, vincristine Bronchodilators and other asthma medications Albuterol, cromolyn sodium, flunisolide, metaproterenol, terbutaline Lipid-lowering drugs Cholestyramine, clofibrate, fluvastatin, gemfibrozil, lovastatin, pravastatin Muscle relaxants and drugs for parkinsonism Baclofen, dantrolene, levodopa Radiation therapy Radiation of the head Suggest Vasodilators a home gas Dipyridamole, nitroglycerin patch detector for REPRINTED WITH PERMISSION FROM SCHIFFMAN SS. TASTE AND SMELL LOSSES IN NORMAL AGING AND DISEASE. JAMA 1997; 278:1357–1362. patients with impaired smell smell abnormalities. Pesticides are also impor- Temporal lobe epilepsy can have compli- tant offenders. cations such as the inability to identify odors. Drugs Psychiatric conditions Drugs in many major therapeutic categories Psychiatric conditions such as depression and have been known to cause smell impairment schizophrenia may also be associated with (TABLE 1). impairment of smell. Neurologic diseases Congenital defects Parkinsonism is frequently associated Some patients complain of the inability to with olfactory dysfunction (dopaminergic smell since birth. In most cases, this is con- medication has no effect on olfaction). genital anosmia,15 a condition in which the Alzheimer disease can present initially with primary receptor neurons either are absent or the problem of anosmia, possibly due to are hypoplastic and lack cilia. However, some- deposits of neuritic plaques in olfactory nerve times the loss may have followed a forgotten pathways.14 Huntington chorea and the head injury or viral infection. Magnetic reso- demyelination of multiple sclerosis can also be nance imaging (MRI) of the brain can con- associated with impairment of smell. firm the absence of the olfactory bulb. CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 69 • NUMBER 4 APRIL 2002 331 SMELL AND TASTE PROBLEMS MANN Autoimmune disorders stage, the patient is given two bottles—a Sjögren syndrome (with accompanying symp- “live” bottle (containing butanol dilution) toms of eye, nasal, and mouth dryness) is often and a “blank”