Anosmia is the medical term for a complete loss of the sense of smell. While changes in smell may seem minor, anosmia can affect taste, appetite, safety, and overall quality of life. Loss of smell can have many causes, ranging from nasal congestion and allergies to infections, head injuries, neurological conditions, and problems affecting the nasal passages.
Understanding what causes anosmia is an important first step toward determining whether the condition can be treated or whether the sense of smell may return on its own.
What Is Anosmia?
What is anosmia? Anosmia is the complete inability to detect odors. A person with anosmia cannot smell food, fragrances, smoke, or other odors that would normally be detectable. Anosmia differs from hyposmia, which means a reduced ability to smell rather than a complete loss.
Because smell contributes to the perception of flavor, anosmia can also make foods seem bland. However, the inability to smell is not the same as losing the basic taste sensations of sweet, salty, sour, bitter, and savory.
What Causes Anosmia?
What causes anosmia? Anosmia can develop when something interferes with the ability of odor molecules to reach smell receptors in the nose, damages the olfactory nerves, or affects the parts of the brain responsible for processing smell.
Common causes include nasal congestion from colds or allergies, chronic sinusitis, nasal polyps, respiratory infections, and structural problems inside the nose. Viral infections can also cause temporary or persistent changes in smell. In some cases, anosmia occurs after a head injury that damages the nerves responsible for transmitting smell signals.
Less commonly, anosmia can be associated with certain neurological disorders. Some medications, smoking, and exposure to certain chemicals may also affect the sense of smell.
Can a Cold or Sinus Infection Cause Anosmia?
Can a cold or sinus infection cause anosmia? Yes. Nasal inflammation and congestion can prevent odor molecules from reaching the olfactory receptors located high inside the nasal cavity. As the infection or inflammation improves, the sense of smell may gradually return.
Chronic sinusitis can be more persistent because ongoing inflammation, swelling, or nasal polyps can continue to interfere with normal airflow and smell detection. Treating the underlying nasal condition may improve the ability to smell.
Can COVID-19 Cause Anosmia?
Can COVID-19 cause anosmia? Yes. Loss or alteration of smell has been associated with COVID-19 and can occur during or after the infection. Some people recover their sense of smell relatively quickly, while others experience persistent changes.
For individuals whose smell remains altered after an infection, medical evaluation can help determine whether another nasal, sinus, neurological, or structural problem may also be contributing to the symptoms.
How Is Anosmia Diagnosed?
How is anosmia diagnosed? Diagnosis typically begins with a medical history and examination of the nose, sinuses, and surrounding structures. A physician may ask when the smell loss began, whether it developed suddenly or gradually, and whether other symptoms are present.
Depending on the suspected cause, testing may include a formal smell identification test, nasal endoscopy, or imaging such as a CT scan or MRI. The appropriate evaluation depends on the individual’s symptoms and medical history.
How Is Anosmia Treated?
How is anosmia treated? Treatment depends on what is causing the loss of smell. If nasal inflammation or congestion is responsible, treatment may focus on the underlying nasal or sinus condition. Depending on the diagnosis, treatment may include medications, management of allergies, or treatment of nasal polyps and chronic sinus disease.
When a structural problem is preventing normal airflow through the nose, a procedure or surgery may sometimes be appropriate. If anosmia follows a viral infection or head injury, recovery may occur gradually, although the outcome can vary.
There is no single treatment that works for every person with anosmia, which is why identifying the underlying cause is important.
What Is Smell Training, and Can It Help Anosmia?
What is smell training, and can it help anosmia? Smell training is a structured approach in which a person repeatedly smells a small selection of familiar odors over time. The goal is to stimulate the olfactory system and encourage recovery or adaptation following certain types of smell loss.
Research has found potential benefits from olfactory training for some people with post-infectious or other forms of smell dysfunction. However, results vary, and smell training should not be considered a guaranteed treatment.
Can Anosmia Be Permanent?
Can anosmia be permanent? Anosmia can sometimes be permanent, particularly when the underlying cause involves significant nerve damage, certain neurological conditions, or severe injury. However, permanent loss cannot always be predicted when anosmia first develops.
Some people experience gradual improvement over weeks or months, depending on the cause. A persistent loss of smell should therefore be evaluated rather than automatically assumed to be permanent.
When Should Someone See a Doctor About Loss of Smell?
When should someone see a doctor about loss of smell? A persistent or unexplained loss of smell warrants medical evaluation, particularly when it develops suddenly or occurs without obvious nasal congestion. Evaluation is also important when anosmia is accompanied by symptoms such as recurrent sinus problems, nasal obstruction, nosebleeds, significant headaches, vision changes, neurological symptoms, or a recent head injury.
Sudden neurological symptoms, including facial weakness, difficulty speaking, severe weakness, confusion, or other signs of a possible stroke, require emergency medical attention.
Why Is Treating Anosmia Important?
Why is treating anosmia important? Treating anosmia can help address an underlying medical problem while potentially improving a person’s ability to smell and enjoy food. Restoring smell can also improve safety because smell helps people detect smoke, spoiled food, gas leaks, and other environmental hazards.
Because anosmia has many possible causes, the most appropriate treatment begins with determining why the loss of smell occurred. For individuals experiencing persistent or unexplained anosmia, evaluation by an appropriate medical professional can help identify the cause and determine the next steps.