Defining smell loss

Making sense of smell disorders

Defining and understanding the causes of smell loss


Many people take their sense of smell for granted. However, even experiencing a reduced sense of smell can affect your quality of life, resulting in deep feelings of loss and, in some cases, isolation and depression. Smell loss affects millions of people worldwide. In fact, it’s been estimated that around 5% of people in the UK are affected by smell loss – that’s around 3.25 million people – with an additional 15% affected by a reduced sense of smell (hyposmia).


How is smell loss defined? 

Anosmia is a complete absence of the sense of smell. It is further defined as acquired or congenital depending on whether or not you had a sense of smell at birth.

Hyposmia is a reduced sense of smell. 

Parosmia is a distorted sense of smell.

Phantosmia is when you experience smells that aren’t there. 

Your sense of smell can also affect your perception of flavour. Many people confuse their smell loss with losing their sense of taste (ageusia); however, taste disorders are much rarer than smell disorders.

What causes changes in your sense of smell?

There are many causes of smell loss. Some create temporary issues while others can lead to long-term problems. They include:

  • An infection, such as a cold, flu or sinusitis

  • Head trauma
  • Allergies, such as hay fever
  • Nasal polyps, which are benign growths in the lining tissues of your nose
  • Ageing, many people experience some loss of sense of smell as they get older
  • Radiation treatment for head and neck cancers
  • Exposure to dangerous chemicals such as pesticides or solvents
  • Abuse of cocaine and other drugs inhaled through the nose
  • Smoking
  • Poor air quality
  • Some neurodegenerative conditions such as Parkinson’s disease, Alzheimer's disease, or brain tumours

In some cases, there is no known cause of smell loss – this is known as ‘idiopathic’ smell loss. Some people are born without a sense of smell and may lack the organs necessary for olfaction. 

How do we experience smell? 

Our sense of smell is a complex partnership between our nose and our brain.

Smell happens when volatile molecules of a substance, for instance a cut lemon, mingle with the air. When they enter our nose, they stimulate olfactory nerve cells found high in the nasal cavity. These nerves send messages to the brain that help us interpret what we are smelling.

Our sense of smell also affects our ability to appreciate food and drink. With a reduced sense of smell, flavours are limited to salty, sweet, sour, bitter and savoury (umami). If you can’t taste food as you used to, anosmia or parosmia could be the cause.

How can smell loss affect your everyday life? 

Our sense of smell is closely related to how we experience and interact with the world. Smell loss can affect everything, including relationships and work life.

There may be fewer practical problems associated with a lost or reduced sense of smell than with loss of sight or hearing. However, studies have shown that many people who have smell loss experience emotional problems and social isolation that can affect every part of their lives.