Anosmia 101
What is anosmia?
Anosmia is the medical term for the loss of the sense of smell. It is far more common than most people realize — and since COVID-19, far more visible than it has ever been. This page covers what anosmia is, what causes it, and the related conditions that often travel alongside it.
The basics
Anosmia is the medical term for the loss of the sense of smell. It can be partial (called hyposmia) or complete. It can be present from birth (congenital anosmia) or develop later in life (acquired anosmia). It can be temporary or permanent, depending on the cause.
Anosmia is not rare. About 5% of the general population has functional anosmia, and roughly 1 in 5 adults will experience some form of smell dysfunction in their lifetime. After COVID-19, those numbers grew significantly — millions of people lost their sense of smell during the pandemic, and a meaningful proportion still haven’t fully recovered.
The two main categories
Congenital anosmia
Congenital anosmia is anosmia present from birth. People with congenital anosmia have never experienced smell. Some forms are linked to genetic syndromes — Kallmann syndrome, CHARGE syndrome (often caused by mutations in the CHD7 gene), and others — while many cases are isolated and not part of a broader syndrome.
Acquired anosmia
Acquired anosmia is anosmia that develops at some point after birth. The most common causes are:
Post-viral infections, including COVID-19, the flu, and the common cold. These remain the leading cause of acquired smell loss worldwide.
Head trauma, particularly injuries that shear the olfactory nerve fibers as they pass through the cribriform plate.
Chronic sinus and nasal conditions, including chronic rhinosinusitis with nasal polyps (CRSwNP) and severe allergies.
Neurodegenerative disease, especially Parkinson’s and Alzheimer’s, where smell loss often appears years before motor or cognitive symptoms.
Aging, which gradually reduces smell sensitivity in most adults.
Certain medications and toxic exposures, including some antibiotics, chemotherapy drugs, and chemical fumes.
Related conditions worth knowing
Parosmia
Parosmia is a distortion of smell, where ordinary smells (often coffee, garlic, meat, or chocolate) become repulsive. It frequently appears during recovery from post-viral anosmia and can last months or years.
Phantosmia
Phantosmia is smelling something that isn’t there — often described as smoke, chemicals, or a burning smell. It can be associated with neurological conditions and warrants medical evaluation.
Hyposmia
Hyposmia is a reduced sense of smell, rather than complete loss.
Ageusia and dysgeusia
Ageusia and dysgeusia are loss and distortion of taste. Because flavor depends heavily on smell, anosmia often feels like a loss of taste — but true taste loss (the ability to detect sweet, salty, sour, bitter, umami) is a separate condition.
Why it matters
Anosmia affects far more than the enjoyment of food. People with smell loss face real safety risks: they can’t smell smoke, gas leaks, spoiled food, or chemical hazards. Anosmia is associated with higher rates of depression and social withdrawal. It changes intimacy — people lose the ability to smell their partner, their child, their home. And because smell is invisible and rarely discussed, the loss is often dismissed by friends, family, and clinicians.
Smell matters. So does the loss of it.
Recovery and rehabilitation
Smell training
Smell training is currently the best-supported intervention for acquired olfactory dysfunction. It is structured, low-cost, low-risk, and backed by a growing body of evidence — particularly for post-viral and post-COVID smell loss.
Questions
Still trying to make sense of it?
Our FAQ covers the questions people ask most — how it’s diagnosed, what causes it, what treatments exist, and what to do next. If you don’t find your answer there, reach out.