Loss of Smell: Causes, Tests, Treatment and Care
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Introduction
Loss of smell may start at once or develop over time 3,5. It can affect food, mood, safety, and daily life 1,4.
Smell helps people notice smoke, gas leaks, and spoiled food 1,4. It also provides much of the flavor linked with eating 1,4.
Many health problems can reduce smell. Examples include viral infections, nasal swelling, polyps, smoking, aging, and head injuries 3,4.
This guide covers loss of smell symptoms, causes, testing, treatment, and when to seek care. It also explains ways to manage the effects at home.
Overview: What Loss of Smell Means
Smell disorders can change odor strength or how odors seem 1,2. Doctors use several terms for these changes.
Anosmia, hyposmia, parosmia, and phantosmia
Anosmia means a complete loss of smell 1,4. It may be brief, long-lasting, present from birth, or acquired later 3.
Hyposmia means a reduced ability to detect odors 1,4. Familiar scents may seem much weaker than before 5.
Parosmia means a real odor smells changed or distorted 1,4. For example, something pleasant may start to smell unpleasant 4.
Phantosmia means sensing an odor when no source is present 1,4. Parosmia and phantosmia change odor quality rather than odor strength 1.
Loss of smell versus loss of taste
Smell and taste work together, but they are separate senses 4. Smell detects airborne odor molecules inside the nose 4.
Taste detects sweet, salty, sour, bitter, and umami 1. These basic tastes often remain when smell is impaired 1.
Many people who report taste loss have impaired flavor instead 1. This happens because smell provides a large part of flavor 1,4.
Food releases aromas during chewing 4. These aromas reach smell cells through a passage between the throat and nose 4.
A blocked passage can make food seem bland 4. Familiar flavors may then become hard to tell apart 4.
How smell changes affect daily life
Smell loss can reduce enjoyment from food and social events 1,8. It may also affect mood, relationships, and physical health 1.
Some people lose interest in eating or experience weight loss 8. Others may avoid meals with family or friends 8.
Smell also serves as an important warning system 4. Reduced smell can make smoke, gas, or spoiled food harder to detect 1,4.
Symptoms and Patterns to Notice
Smell disorders include reduced, absent, distorted, or phantom odors 1,4. The pattern can offer clues about the cause 1,2.
Common symptoms of smell disorders
A change in familiar scents may be an early sign 5. A favorite soap or perfume may smell weaker than before 5.
Common loss of smell symptoms may include the following changes:
Familiar scents seem weaker, which matches the meaning of hyposmia 4,5.
No odors can be detected, which matches the meaning of anosmia 1,4.
A real scent smells different, strange, or unpleasant 1,4.
An odor seems present when no source can be found 1,4.
Food seems bland because smell provides much of its flavor 4.
Familiar flavors become harder to identify even when basic tastes remain 1,4.
Some people do not notice their own smell problems 2,6. Formal smell loss testing can measure changes that a person may miss 1,2.
Sudden, gradual, and one-sided smell loss
Sudden smell loss can follow a viral infection or head injury 3. COVID-19 and other viral infections can cause a sudden decline 1,2.
Smell loss may begin at once or later after an injury 2. Trauma may harm the nose, smell nerves, or brain pathways 2,3.
Gradual loss can occur with allergic rhinitis, polyps, or tumors 3. Rhinitis means swelling and irritation inside the nose.
Aging may also reduce smell over time 3,4. However, sudden loss is less likely to result from aging alone 10.
Symptoms can remain steady or change from day to day 1,2. Allergic rhinitis may cause smell loss that comes and goes 3.
Doctors also ask whether one or both sides seem affected 1. Onset, duration, severity, and laterality can guide the assessment 1.
Laterality means whether symptoms affect the left side, right side, or both sides.
Symptoms that may point to the cause
Nasal blockage, discharge, and facial pressure may occur with rhinosinusitis 2. Rhinosinusitis means swelling within the nose and sinuses.
A sudden change after a viral illness may suggest post-infectious smell loss 2. Parosmia can also occur after a viral illness 2.
Phantosmia may occur after a head injury 2. Signs of trauma or nerve problems may lead to more testing 6.
These details can help a clinician understand the symptom pattern:
Record whether the change began at once, slowly, or after an event 1,2.
Note whether symptoms stay steady, improve, worsen, or come and go 1,2.
Describe whether smells are absent, weak, distorted, or present without a source 1,2.
Note any blockage, discharge, sneezing, or pressure around the face 2.
Record recent illness, injury, surgery, smoking, or chemical contact 1,2.
Explain any effects on eating, mood, work, and home safety 1,2.
Causes of Loss of Smell
Smell loss can result from blockage, damaged smell cells, or affected brain pathways 1,3. Nose and sinus disorders cause a large share of acquired smell loss 1,3.
Nasal blockage, inflammation, and infection
Nasal disease can stop odor molecules from reaching smell cells 1,3. Swelling may also harm the tissue that detects odors 3.
Common nose, sinus, and infection causes include these conditions:
Colds and influenza can cause blockage and smell loss 4,5.
COVID-19 can cause smell loss that is brief or long-lasting 1,7.
Allergic rhinitis can cause swelling, blockage, and changing smell ability 3,6.
Rhinosinusitis can reduce smell through swelling and blocked airflow 2,3.
Nasal polyps can block airflow and stop odors from reaching smell cells 3,5.
A deviated septum can block nasal airflow and affect smell 5,7.
Sinonasal disease affects the nose and sinuses. It includes rhinitis, chronic rhinosinusitis, polyps, and other forms of blockage 1,3.
Injury, medicines, smoking, and chemical exposure
A head injury can harm several parts of the smell pathway 3. Damage may affect the nose, skull base, smell nerves, or brain 2,3.
Injury-related loss can be temporary or permanent 3. Improvement is less likely after trauma than after treatment of a reversible cause 6.
Smoking can affect the sense of smell 4,7. Long-term tobacco use may raise this risk 7.
Some chemicals can also impair smell 3,4. Listed examples include insecticides, solvents, and toxic vapors 3,4.
Radiation for head or neck cancer can lead to smell loss 4,7. Some medicines may also cause smell changes 3,4.
Reported medicine groups include certain antibiotics and antihistamines 3,4. Some blood pressure and thyroid medicines are also listed 3.
Do not stop a prescribed medicine without medical guidance. Ask the prescriber to review possible side effects and treatment choices.
Aging, neurologic disease, and rare causes
The sense of smell tends to weaken with age 3,4. Aging can reduce smell cells and tissue within the smell system 3.
Some diseases of the brain and nerves can affect smell 3,7. These include Parkinson disease, Alzheimer disease, and Lewy body dementia 3,7.
Smell changes may be an early sign of Parkinson disease or dementia 6. Yet many common nasal problems can also impair smell 4,6.
Less common anosmia causes include tumors and conditions present from birth 3,4. Hormone problems may also cause smell disorders 4.
Diabetes and low thyroid function can cause reduced smell in uncommon cases 3. Growths inside the nose or brain can block smell pathways 3,4.
How Loss of Smell Is Tested
Evaluation starts with a medical history and physical examination 1,2. Some people also need smell testing, nasal endoscopy, or scans 1,6.
Medical history and physical examination
A clinician will ask how and when the change began 1,2. Questions may cover severity, duration, daily patterns, and effects on life 1,2.
The history may include the following useful topics:
Recent colds, COVID-19, other infections, and ongoing nasal symptoms 1,2.
Nasal blockage, discharge, sneezing, facial pressure, and known polyps 2,6.
Head injuries, nasal surgery, cancer care, and other past procedures 1,2.
Medicines, supplements, smoking, and contact with harmful chemicals 1,2.
Changes involving appetite, weight, food pleasure, mood, and safety 1,2.
Distorted odors, phantom smells, flavor changes, and basic taste 1,2.
The examination may cover the ears, nose, throat, mouth, head, and nerves 4,6. Anterior rhinoscopy means looking inside the front of the nose 6.
This examination may show swelling, mucus, bleeding, enlarged tissue, or a mass 6. A nerve examination may follow trauma or abnormal nerve findings 6.
Nasal endoscopy and objective smell tests
Nasal endoscopy uses a thin viewing tool to look deeper inside the nose. It can show swelling, discharge, polyps, scars, crusting, or masses 1.
Endoscopy may find nasal disease missed during a basic examination 6. It also shows areas near smell tissue and sinus openings 1.
Psychophysical testing uses set odors and records each response 1,2. The person must understand the directions and report each choice 2.
Validated smell loss testing can measure three key abilities:
Odor threshold testing finds the smallest amount of odor someone can detect 2,4.
Odor identification testing checks whether someone can recognize a scent 2,4.
Odor discrimination testing checks whether someone can tell odors apart 2.
These tests measure smell ability and track change over time 1. Several test parts may also show patterns linked with certain causes 2.
When CT, MRI, or other tests are considered
Scans are often not needed for common, treatable causes without trauma 6. The history and examination help guide the choice 1,6.
A computed tomography scan is also called a CT scan. CT can examine the sinuses and skull base 2.
Sinus CT may show polyps or hidden sinus changes 2. It is the preferred scan when more sinus testing is needed 6.
Magnetic resonance imaging is also called MRI. It creates detailed images of the head.
MRI may be used after trauma or an abnormal nerve examination 6. It may also be used when a tumor is suspected 6.
Special tests may include smell-evoked signals or functional MRI 1. These tests are mainly used in research rather than routine care 1.
Treatment for Loss of Smell
Loss of smell treatment depends on the cause 4,5. Treating a reversible problem may help smell return 6.
Treating the underlying cause
Treatment for nasal swelling may improve the movement of odors 3,6. The right choice depends on the diagnosis and medical needs.
Possible cause-based forms of care include the following options:
A clinician may select treatment for allergies or sinus swelling 6.
An identified infection may receive suitable treatment 5.
A clinician may review medicines linked with smell changes 4,5.
Surgery may remove a polyp or correct another blockage 5,7.
Reducing contact with smoke or harmful chemicals may limit further exposure 2,4.
Nasal or oral corticosteroids may treat some nose and sinus conditions 6. These medicines can reduce swelling and improve odor movement 6.
Evidence for medicine after viral smell loss is limited 6. Treatment choices should follow a personal medical assessment.
Smell training
Olfactory training means repeated, focused exposure to chosen odors 6. Olfactory is the medical word related to smell.
Smell training may improve smell function in some people 6. It is one treatment used for ongoing smell disorders 7.
Results and recovery times can differ 6,7. A clinician or ear, nose, and throat specialist can explain this option.
Everyday safety
Smell loss can hide smoke, gas leaks, and spoiled food 1,4. Simple habits can help address these risks.
Useful safety steps include the following practical actions:
Check that smoke alarms and other home alarms work 6.
Follow printed food expiration dates instead of smell alone 6.
Ask someone else to check food when its condition seems uncertain.
Use labels to help track when leftovers were stored.
Use timers while cooking instead of depending on food odors.
Tell household members that smell loss may affect hazard detection.
When to See a Doctor for Loss of Smell
See a clinician if smell does not return after a cold or influenza clears 5. Ongoing anosmia may need more assessment 5.
Sudden smell loss that does not improve also needs medical review 10. A sudden change is less likely to reflect aging alone 10.
These situations support arranging a medical appointment:
Smell remains reduced after a respiratory illness has ended 5.
The change began suddenly and has not improved 10.
Symptoms started after a head injury 2,3.
The problem keeps getting worse or mainly affects one side 1.
Nasal blockage, discharge, facial pressure, bleeding, or a mass is present 2,6.
Smell loss affects appetite, weight, mood, work, or home safety 1,2.
Distorted or phantom odors continue to disrupt daily life 1,2.
The supplied sources do not give emergency rules for isolated smell loss. This article therefore avoids assigning emergency care without direct support.
Recovery and Living With Smell Loss
Recovery depends on the cause 5,6. Smell can return after a brief blockage or treatable nasal problem improves 5,6.
How long recovery may take
Smell loss from a cold or sinus infection is often temporary 5. Smell may return when the illness or blockage clears 5.
COVID-19 smell loss may improve within weeks 7. In some cases, recovery takes months or longer 7.
Some smell loss after infection may remain permanent 1. Recovery after head trauma may also be incomplete 3,6.
Improvement is less likely with trauma, aging, or diseases affecting the brain 6. This makes a clear diagnosis important.
Nutrition, mood, and quality of life
Ongoing smell loss can reduce food pleasure and interest in eating 8. It can contribute to weight loss and nutrition problems 8.
Smell disorders may also affect mood and relationships 1. Some people avoid meals and social events because food feels less rewarding 8.
Tell a clinician about appetite changes, weight loss, or low mood. These problems may support specialist referral or formal smell testing 6.
Preparing for a medical appointment
Clear notes can help the clinician understand the problem. Prepare the following details before the visit:
Write down when the change started and how quickly it developed 1,2.
Record whether it stays steady, improves, worsens, or comes and goes 1,2.
List recent illnesses, injuries, nasal symptoms, surgeries, and chemical exposures 1,2.
Bring a current list of medicines and supplements 2,6.
Note changes in flavor, appetite, weight, mood, and home safety 1,2.
Describe distorted smells, phantom odors, and one-sided symptoms 1,2.
An ear, nose, and throat doctor is also called an ENT specialist 4. This doctor may suggest endoscopy, smell testing, CT, or MRI 1,6.
Conclusion
Understanding loss of smell symptoms, causes, testing, treatment, and when to seek care supports informed choices. Common causes include infections, nasal disease, polyps, smoking, aging, and head trauma 1,3,4.
Many reported taste problems actually involve impaired flavor 1,4. Basic tastes often remain even when smell is reduced 1.
Formal tests can measure odor threshold, identification, and discrimination 1,2. CT and MRI are chosen based on the suspected cause and examination findings 1,6.
Treatment aims to address the underlying cause 4,5. Smell training may help some people, but recovery and results vary 6,7.
Persistent or unexplained smell loss should receive medical assessment 5,10. Evaluation may find treatable causes and help address safety or nutrition concerns 1,6.
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