What is anosmia? Why losing your sense of smell matters more than you think

Of the five senses, smell is the one people say they would give up first, ranking it below sight, hearing, taste and touch. Yet those who actually lose it describe a diminished, sometimes disorienting world. A feature in Ars Technica examines anosmia, the loss of the sense of smell, and explains why a sense long dismissed as minor turns out to matter a great deal.

Anosmia can be total or partial, temporary or permanent. It arises from many causes: viral infections, head injuries, nasal and sinus disease, certain neurological conditions and, in some cases, no identifiable reason at all. The COVID-19 pandemic dramatically raised public awareness, as sudden loss of smell became one of the illness's most recognisable symptoms and left some people with lingering problems.

The first thing people notice is usually food. Much of what we call flavour is actually smell; the tongue detects only basic tastes such as sweet, salty, sour, bitter and savoury, while the nose supplies the richness and complexity. When smell disappears, meals can feel flat and joyless, which in turn can affect appetite, nutrition and the simple pleasure of eating.

Safety is a less obvious but serious concern. Smell warns us of danger, including smoke, gas leaks and spoiled food. People with anosmia can miss these signals entirely, and the feature notes that this loss of an early-warning system is one of the practical hazards that make the condition more than a mere inconvenience.

There is also a profound emotional dimension. Smell is wired closely to the brain's centres for memory and emotion, which is why a particular scent can summon a vivid memory in an instant. Losing that channel can feel like losing a connection to the past and to other people, and some who experience anosmia describe a sense of detachment or low mood that surprises those around them.

A particularly distressing variant is parosmia, in which smells become distorted rather than absent. Foods and everyday scents can take on foul, unpleasant qualities, turning ordinary experiences into ordeals. Parosmia often appears as smell begins to recover after an infection, and it can be more disturbing than the original loss.

For a long time, medicine paid relatively little attention to smell. It was harder to measure than vision or hearing, and treatments were limited. That has begun to change. Researchers have developed better ways to test smell, and interest in how the olfactory system works, and how it might be repaired, has grown, spurred in part by the wave of pandemic-related cases.

One of the more hopeful developments is smell training, a technique in which people repeatedly sniff a set of distinct scents over weeks or months in an effort to help the system recover. It does not work for everyone, and results vary, but it reflects a broader recognition that the olfactory system has some capacity to regenerate, unusual among the body's sensory pathways.

Understanding smell also has scientific value beyond treating its loss. The olfactory system is a window into how the brain processes information, forms memories and links sensation to emotion. Studying what happens when it fails can illuminate how it works when it functions normally.

The broader message of the Ars Technica piece is a reappraisal. Smell has been treated as the expendable sense, but for those who lose it, the effects reach into eating, safety, memory and mood. As research advances, anosmia is being recognised not as a trivial complaint but as a genuine medical condition, one that deserves the attention it long went without.