Diagnosis and Treatment of Distorted Olfactory Perception

There are three types of human olfactory dysfunction: (1) decreased ability to perceive odorants (hyposmia, anosmia); (2) distorted quality of perceived odorants (troposmia, derived from trop,“to turn or react,” and osmia); and (3) perceived odor when no odorant stimulus is present (phantosmia, hallucination). Patients with only hyposmia or anosmia generally complain of decreased ability to smell odorants and appreciate foods, but the quality of the perceived odors is “normal” for the patient. Although patients with troposmia, phantosmia, and hallucinations may have decreased ability to perceive odorants, their main concern is that perceived odors are distorted or different from what they remember.