Loss of smell: causes of anosmia, including with a cold

The child is sniffling again, and you open a jar of jam and feel nothing. Then you try the soup: it seems salty, and then again it doesn't. The picture is familiar, especially during cold season, and in most cases it is reversible.

How smell works

Molecules of odorous substances must reach the olfactory receptors — they lie high in the nose, in a narrow cleft under the very roof of the nasal cavity. Then the signal travels along the olfactory nerve to the brain, and there it is turned into "this is borscht" or "this is gasoline." A failure can occur at any point: air does not pass because of swelling or a polyp, the receptors are damaged, the nerve or the conducting pathways are affected. Hence two large groups of causes — mechanical and neural.

What anosmia is

Anosmia is the loss of smell, most often complete. In practice, partial, selective anosmia is more common, when a person cannot smell only certain substances. A reduced sensitivity to smells is called hyposmia, and a distorted perception of them is called parosmia. Loss of smell can be congenital or acquired.

Causes of loss of smell

The list is long, and some items have nothing to do with smell itself — they simply prevent air from passing through the nose.

• Nasal congestion: a cold, rhinitis, sinusitis, pollen allergy, polyps, deviated septum, nasal tumors.
• Viral infections, including COVID-19, in which the neural pathways are affected.
• Head trauma, surgery on the nose and sinuses, radiation to the head and face.
• Medications that alter the perception of smells, including prolonged use of decongestant drops.
• Age, smoking, nutritional deficiencies, endocrine disorders, toxins, neurological diseases — from Parkinson's disease and Alzheimer's to dementia with Lewy bodies.

Often the cause is never found: in most cases there is no clear explanation.

Loss of smell with a cold and after coronavirus

With a cold and nasal allergy, loss of smell is usually temporary: the mucosa is swollen, air does not reach the receptors, and smells return when the congestion subsides. After a viral infection, smell often returns on its own, but not immediately. If the loss of smell and taste lasts longer than 12 weeks after COVID-19, it may be one of the manifestations of post-COVID syndrome: among its symptoms are changes in taste and smell, tinnitus, and problems with vision and hearing. In that case the person is referred to a doctor, and the care program includes support in trying to improve smell.

Why taste disappears along with smell

Smell enhances taste — and this is not a figure of speech. Those who have stopped smelling often complain that taste has disappeared too. At the same time, most still distinguish salty, sweet, sour, and bitter: these sensations are provided by the tongue. But subtle nuances — coffee, fried food, spices — cannot be recognized. Some spices, such as pepper, act on the nerves of the face, and are more felt than smelled.

How diagnosis is carried out and when to see a doctor

The doctor examines the nose and asks questions: when the problem appeared, whether all smells disappeared or only some, whether taste was affected, whether there are symptoms of a cold or allergy, what medications the person takes, and whether there are other complaints. Possible examinations include CT and MRI, nasal endoscopy, testing of the olfactory nerve, and smell identification tests. You should see a doctor if the loss of smell continues or worsens, as well as with other unexplained symptoms.

Loss of smell by itself is not a reason to call an ambulance; 103/112 — for signs of stroke or heart attack or another life-threatening condition.

This material is for reference: it does not replace a doctor's consultation, so if in doubt it is better to see an otorhinolaryngologist.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer