What happens when you lose your sense of smell?

Imagine living without your sense of smell; you couldn’t smell the toast you’ve forgotten as it burns under the grill, the flowers and freshly cut grass in the spring, or whether the milk in your fridge that’s a day past its before end will curdle in your cup of tea.

Smell is key to everyday life. It helps us avoid danger, influences our emotions and triggers memories. “A good sense of smell is vital for physical and mental health, and social wellbeing,” said Professor Carl Philpott, from the University of East Anglia’s (UEA) Norwich Medical School.

But smell dysfunction, where the ability to smell is reduced, distorted or lost completely, is present in over 130 different neurological, physical and inherited conditions, with some evidence suggesting a causal role.

Researchers from UEA describe smell as a Cinderella sense, one where research is lagging behind sight and hearing in terms of its perceived importance. They believe a national smell screening programme could improve the mental and physical health of millions of people.

“Smell health underpins good nutrition, cognitive function, and psychological resilience. But national public health agendas around the world rarely consider smell health,” Philpott added.

What goes wrong?

Smelling involves your nose and your brain, and the communication between them. The inside of your nose is covered with olfactory neurons which send messages to your brain about the scents – good and bad – they detect. When the message reaches your brain, it recognises it and identifies the smell, but if there is a problem or blockage anywhere in this signalling pathway, the ability to smell will be affected.

Loss of smell might be subtle and slow or happen very quickly. It’s usually linked to a loss of taste, or ageusia, as the two are closely linked and both involved in the ability to taste flavours.

Common causes for olfactory dysfunction include chronic rhinosinusitis (CRS), head and neck cancers, infections of the upper respiratory tract including COVID, and head trauma (post-traumatic olfactory dysfunction—PTOD); but for some, the cause is unexplained. It can be treated with medication, retraining therapy or surgery, but in some cases, the loss of smell can be permanent.

Why is it a problem?

Experiencing a loss of smell can be frustrating – you can’t smell the freshly baked chocolate brownie, or the sea salt at the beach – but it can also be a real problem as your sense of smell acts as your first warning system against burning or fire, gas leaks, and spoilt or rotten food.  My brother developed anosmia – a total loss of smell – during the onset of ME and once had the fire brigade round as he’s knocked the knob on the cooker while cleaning and his whole flat smelt of gas.

But it can also take a toll on your quality of life. There are high rates of eating disorders among those with olfactory dysfunction, but evidence also suggests those with parosmia (smell distortion) and anosmia or hyposomia (partial smell loss) often consume a poor-quality diet, full of energy-dense, high fat, high sugar foods.

Olfactory dysfunction can also impact people’s mental health, with reports of social isolation, relationship difficulties, anxiety and depression common. Data suggests that managing the psychological effects of the condition contributes to an estimated annual drug cost of 8.3 million antidepressant prescriptions in the UK.

Putting smell on the map

Anosmia was a common symptom of the early Covid-19 strains, but smell disorders are actually very common, occurring in at least 139 neurological, physical, and inherited conditions, Philpott explained: “Research suggests smell loss may play a causal role because it often appears early and can predict future health issues. Increasing evidence has shown that smell loss is an independent risk factor for neurodegenerative disorders, increased frailty and reduced longevity.”

In their recent paper, Philpott and colleagues concluded that many medical conditions are linked to olfactory dysfunction including Alzheimer's and Parkinson's disease, where anosmia occurs over 90% of patients up to five years before clinical motor symptoms appear.

However, the rate of olfactory dysfunction is likely underreported because of a lack of screening or routine testing in secondary care; the paper says anosmia is more prevalent than reported rates of profound hearing loss or blindness and affects ~5% of the population. Overall, olfactory dysfunction affects around 22% of the population, and increases with age, particularly among men.

Yet smell disorders are “under-rated, under-researched, and under-treated,” Philpott said. Philpott and his colleagues are calling for a worldwide campaign to put smell health on the map, with screening, education and awareness central to the campaign.

“The sense of smell should be promoted as an essential pillar of health, as it enables good nutrition and cognitive and psychological well-being,” Philpott said. “We recommend developing smell health educational programmes and awareness campaigns, introducing smell screening and developing and implementing smell health policies across all sectors of society.”

The screening programmes would help researchers detect olfactory dysfunction and help them better understand its pathophysiology; this would help with the development of new therapeutic options, which are urgently needed. Screening would also improve education among medical students, healthcare professionals and social workers who currently receive little or no education on the topic of smell and taste and their related disorders.

“The good news is that simple techniques like smell training, using everyday items from your cupboard, can help restore scents and improve quality of life. Smell retraining and therapies like vitamin A nasal drops offer hope, but we need more investment and awareness to help those living with long-term loss,” Philpott said. “For thousands, it’s still a daily struggle. Recovery isn’t guaranteed, and that’s why research matters.”

Sources

The Need to Promote Olfactory Health in Public Health Agendas Across the Globe, Clinical Otolaryngology, 2025. Philpott C.M., et al.

New review highlights urgent need for worldwide smell screening, UEA.

A feast without flavour: The hidden impact of smell and taste loss at Christmas, UEA.

Anosmia: Loss of smell, Stanford Medicine Health Care.