Loss of Smell

Loss of smell is the inability to smell as well as before or the inability to smell at all. Partial reduction is called hyposmia, while complete loss is termed anosmia. Many people first describe this complaint by noticing that the flavor of food seems significantly reduced, because the sense of smell is an important part of flavor perception. For that reason, loss of smell is not merely a “nasal” complaint; it can also affect appetite, nutrition, quality of life, and safety. ^[1][2]

MedlinePlus notes that temporary loss of smell is common in upper respiratory conditions such as the common cold and allergic rhinitis. However, loss of smell is not always short-lived. Obstructions that prevent air from reaching the smell receptors inside the nose, receptor damage, head trauma, aging, some neurologic diseases, and more rarely congenital conditions may also lead to this symptom. For this reason, the duration of the problem and associated symptoms are decisive in evaluation. ^[3][4]

What does loss of smell mean?

Loss of smell may sometimes simply reflect nasal congestion, and at other times it may suggest involvement of the smell pathways or the nervous system. In nasal congestion, sinusitis, polyps, and allergies, air does not adequately reach the smell receptors. Viral infections may affect olfactory cells directly. According to NIDCD, smell disorders may appear not only as reduced ability to detect odors but also as altered odor perception. For that reason, the complaint may present not only as “I cannot smell anything,” but also as “things smell different than before.” ^[2][3]

Loss of smell can seriously affect everyday life without a person fully realizing it. It may become harder to detect smoke, gas leaks, spoiled food, or personal hygiene cues. In addition, reduced appetite, weight loss, loss of enjoyment of food, and low mood may occur. Mayo Clinic emphasizes that loss of smell can affect appetite, dietary habits, and safety. For that reason, it should not be minimized as “not dangerous”; especially when prolonged, it matters from a quality-of-life standpoint. ^[1][4]

What causes loss of smell?

The most common causes include the common cold, allergic rhinitis, sinusitis, and other conditions that produce nasal congestion. As these conditions improve, the sense of smell may also recover in many people. Other causes include nasal polyps, head trauma, older age, certain medications, and neurologic diseases. NIDCD reports that smell disorders are more common with advancing age and may be more prevalent in men. This does not mean that loss of smell should automatically be considered normal in every older adult; new-onset changes still deserve evaluation. ^[2][3]

Sudden loss of smell and smell that gradually declines over years are not approached in the same way. Sudden loss is more often associated with infection or acute intranasal processes, whereas slowly progressive decline may be related to age-related changes, chronic nasal disease, or some neurologic causes. More careful investigation is warranted when there are additional findings such as headache, visual change, one-sided nasal obstruction, recurrent nosebleeds, or a history of head trauma. ^[1][3][4]

Why are associated findings important?

If loss of smell is accompanied by runny nose, congestion, facial pain, a pressure sensation, or sneezing, nasal and sinus causes become more likely. By contrast, clear changes in taste, dizziness, neurologic symptoms, or a history of head trauma shift the direction of evaluation. Smell disturbance can sometimes arise not from a local nasal problem, but from involvement of the olfactory nerve or the related brain pathways. ^[2][3]

In some people, smell dysfunction may take the form of parosmia or phantosmia—that is, distorted smells or sensing odors that are not actually present. Although these may seem distinct from the usual heading of “loss of smell,” they are important because they involve the same sensory system. Medical evaluation is needed especially if the changes are new, prolonged, or cause nutritional problems or safety risks. ^[2][4]

What is assessed during the diagnostic process?

During evaluation, clinicians ask whether the complaint developed suddenly, whether there was an upper respiratory infection, whether nasal congestion, allergy, chronic sinusitis, trauma, or medication use is present. On examination, the nasal passages, signs of polyps or inflammation, sinus tenderness, and neurologic findings are assessed. When needed, an ear-nose-throat evaluation, smell testing, or imaging may be planned. Not every patient requires the same tests, because the range of possible causes is broad. ^[2][3]

Reduced smell is more common after age 60; however, before attributing the complaint to age alone, potentially reversible causes should be excluded, and its impact on daily life should also be assessed. Individualized medical evaluation is important when loss of smell is prolonged, progressively worsening, associated with one-sided nasal findings, or accompanied by neurologic signs. In some cases, the symptom may be related to chronic sinus disease, structural blockage, or more rarely neurologic causes. ^[2][4]

When is more rapid evaluation needed?

More rapid evaluation is needed if loss of smell began after head trauma, occurs together with severe headache, visual changes, neurologic symptoms, one-sided obstruction, or recurrent nosebleeds. Likewise, it is not appropriate to wait if loss of smell is markedly impairing nutrition, making it difficult to distinguish spoiled food, or simply failing to improve over time. ^[3][4]

Although loss of smell is often related to upper respiratory and intranasal causes, it does not always mean a simple blockage. Particularly when complaints are prolonged, recurrent, or associated with neurologic findings, specialist evaluation offers a safer, clearer, and more systematic path. ^[1][2]