Parosmie

Parosmia, also known as parosmie in some languages, is a qualitative olfactory disorder in which odors are distorted. People with parosmia may find that familiar smells—such as coffee, meat, or perfume—smell unpleasant, burnt, or otherwise altered, and the distortion can vary over time. It often accompanies a reduced sense of smell (hyposmia or anosmia) following damage to the olfactory system.

Causes and mechanisms: Parosmia frequently follows viral upper respiratory infections, including COVID-19, or results from nasal or sinus disease, head trauma, or sinonasal surgery. The underlying mechanisms are not fully understood but are thought to involve damage to olfactory receptor neurons and their regrowth, miswiring within the olfactory epithelium, or changes in central olfactory processing.

Clinical features: In addition to distorted odors, patients may experience intermittent symptoms and odor triggers that are unpredictable. Parosmia is distinct from phantosmia (smelling odors that are not present) and from a complete loss of smell.

Diagnosis: Diagnosis is primarily clinical, based on history and symptom description. Objective olfactory tests such as the Sniffin’ Sticks or the University of Pennsylvania Smell Identification Test (UPSIT) can assess overall olfactory function and help characterize the degree of impairment. Imaging is not routinely required.

Treatment and prognosis: There is no universally proven cure. Olfactory training—repeated, structured exposure to a set of odors (for example, rose, lemon, clove, eucalyptus) over several months—is commonly recommended and may improve outcomes. Management of underlying nasal inflammation or disease is also advised. Some individuals recover gradually over time, while others experience persistent symptoms.