Smell disorders include a loss in the ability to smell or changes in the way odors are perceived. Hyposmia is when the ability to detect odor is reduced. Anosmia is when a person can't detect odor at all.
Some people experience change in the perception of odors, or notice that familiar odors become distorted, or may perceive a smell that is not present at all.
Smell disorders have many causes including illness including upper respiratory infection, injury, polyps in the nasal cavities, sinus infections, hormonal disturbances, dental problems, exposure to certain chemicals such as insecticides and solvents, some medicines, and radiation due to head and neck cancers. Obesity, diabetes, hypertension, malnutrition, Parkinson's disease, Alzheimer’s disease, multiple sclerosis and Korsakoff syndrome (also called Korsakoff psychosis) are all accompanied or signaled by chemosensory problems like smell disorders. Surgery may be recommended when nasal polyps are the cause of the smell disorder.