The loss of smell is usually an insignificant result of nasal congestion or obstruction, but it can sometimes indicate a neurological disorder. Loss of the sense of smell may be idiopathic (without any identifiable cause). Some loss of smell occurs normally with aging. In most cases, there is no obvious or immediate cause, and there is no treatment. Temporary loss of the sense of smell is common with colds and nasal allergies, such as hay fever (allergic rhinitis). It may occur following a viral illness. The sense of smell is often lost with disorders that prevent air from reaching the part of the nose where smell receptors are located (the cribriform plate, located high in the nose). These disorders may include nasal polyps, nasal septal deformities, and nasal tumors. Other disorders that may cause a loss of the sense of smell include tumors of the head or brain, head trauma, and a wide variety of endocrine, nutritional, Alzheimer's dementia, and nervous disorders. Many medications may change or decrease the ability to detect odors. Most people who lose the sense of smell can still differentiate salty, sweet, sour, and bitter tastes, which are sensed on the tongue. They may not be able to distinguish other flavors. Some spices (such as pepper) may stimulate facial nerves and may be felt rather than smelled.
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