Parosmia

Parosmia is a qualitative olfactory disorder in which familiar odors are distorted or experienced differently than usual. Rather than a complete loss of smell, people with parosmia perceive smells as unpleasant or altered, often described as burnt, rotten, chemical, or sulfurous. Common triggers include everyday scents such as coffee, meat, onions, toothpaste, or perfume, and the distorted experience can fluctuate over time.

Most cases arise during recovery from loss of smell after a viral upper respiratory infection, including COVID-19. The prevailing explanation is that damage to the olfactory receptor neurons in the nasal mucosa during illness is followed by imperfect regeneration, leading to distorted signaling to the brain. Parosmia can also follow chronic sinus disease, head trauma, or exposure to certain toxins, though it may occur without a clear preceding event.

Diagnosis is clinical, based on history and examination. Objective olfactory tests can help characterize the degree of dysfunction and distinguish parosmia from other smell disorders; imaging is not routinely required unless there are additional neurological concerns.

Management focuses on coping and promoting recovery of olfactory function. Olfactory training, which involves repeated, daily exposure to a set of odors (for example, rose, lemon, eucalyptus, and clove) for several months, has the best-supported evidence and is commonly recommended. Short courses of corticosteroids are sometimes tried early after onset, but evidence for their effectiveness is limited. Safety precautions, such as checking for gas leaks or spoiled food, may be advised while smell returns.

Prognosis varies; many individuals gradually improve over months, but some experience persistent distortions. Parosmia can significantly impact appetite, food enjoyment, and quality of life.