Many individuals with olfactory disorders report a decreased quality of life, particularly those with severe olfactory dysfunction . Olfaction plays a significant role in our detection of the aroma and flavor of foods. It is also responsible for our awareness of fragrances in the 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 . 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 . Some individuals with olfactory disorders find it difficult to function in everyday life .
The evaluation of patients with abnormalities of taste or smell requires a multidisciplinary approach which may include the primary care clinician, otolaryngologist, neurologist, allergist, and oral consultant. The approach to these patients is reviewed here. The anatomy of taste and olfaction and the causes of abnormalities in these areas are discussed separately. (See "Anatomy and etiology of taste and smell disorders".)
HISTORY AND PHYSICAL EXAMINATION
A number of features in the patient's history can be useful in evaluating disorders of smell or taste (table 1 and table 2).
- Head injuries  or viral infections  often produce sudden smell loss; in comparison, allergic rhinitis, nasal polyps, or neoplasms are associated with more gradual onset .
- Impairment that is intermittent is often seen in allergic rhinitis and the use of topical drugs.
- Associated symptoms such as headache and behavior disturbances may indicate problems with the central nervous system .
In addition, occupational exposure (chemicals, toxic fumes) and tobacco and alcohol habits need to be explored [9,10]. Allergies and medications also may be causally related (table 3 and table 4).