The most common sensory complaints are a loss of the sense of smell and the sense of taste. Testing may demonstrate a reduced ability to detect odours, or to taste sweet, sour, bitter or salty substances. Some people can detect no odours or no tastes. The sense of smell is most accurate between the ages of 30 and 60 years. A natural decline in smelling ability typically occurs after age 60.
Many people develop a taste or smell disorder as a result of an injury or illness.
Upper respiratory tract infections or an injury to the head are sometimes responsible for smell or taste problems. Loss of smell or taste may result from polyps in the nasal or sinus cavities, hormonal disturbances or dental problems. Prolonged exposure to certain chemicals such as insecticides or some medicines can also play a key role. Tobacco smoking impairs the ability to identify odours and diminishes the sense of taste. Many persons who receive radiation therapy for cancers of the head and neck later complain of lost smell and taste.