Prevention & care
Smell and taste changes: loss, distorted odors, flavor and recovery evidence
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Smell can be reduced, absent or distorted. Smelling an odor that is not present is another kind of change. These experiences describe different symptoms, not a single diagnosis.[1]
Different words describe different smell experiences
Hyposmia means reduced smell; anosmia means absent smell. Parosmia means an odor that is present smells distorted, such as a familiar food smelling unpleasant. Phantosmia means perceiving an odor without an outside source. Explain which experience occurs rather than reporting every change as complete loss.[1]
Food flavor is more than taste on the tongue
Taste includes sweet, sour, salty, bitter and umami. Food flavor also draws on smell, temperature and texture. Many people reporting lost taste actually have impaired smell. Hypogeusia means reduced taste and ageusia means absent taste; dysgeusia includes persistent unpleasant or metallic taste.[2]
History and examination help distinguish causes
A clinician may review infections, head injury, medicines, chemical exposures and nasal symptoms, and examine the nose, mouth or teeth. Supervised smell testing can measure detection or identification. A smell complaint alone cannot identify which of these causes applies.[1]
Persistent change deserves assessment and practical support
The NHS advises seeing a GP when smell has not returned to normal within a few weeks. Nasal conditions may need cause-specific care, and unclear cases may be referred. Recovery can take weeks or months, and some changes persist. No fixed recovery date follows from the symptom label.[3]
True taste problems may need oral and medicine review
Taste disorders can follow some medicines, dental problems, infections or head-and-neck treatment. Assessment may include oral examination and supervised taste tests. Discuss suspected medicine effects with a clinician; do not stop a prescribed medicine on the strength of a taste change alone.[2]
Use other safeguards when smell is unreliable
Impaired smell can remove warnings of fire, escaping gas or spoiled food. A practical response is to use functioning alarms and established food-storage guidance rather than relying on a sniff test.[3]
Discuss disrupted eating or wellbeing with a clinician. Adding extra salt or sugar can create problems, particularly with conditions such as hypertension or diabetes.[2]
Evidence & uncertainty
Evidence for persistent smell loss after COVID-19 has changed over time. A Cochrane review searched through October 2021 and found only two small treatment studies with very uncertain results. Its findings cannot summarize trials published later.[7]
Selected-source overview · Independent review pendingPublished questions
Why does familiar food smell unpleasant instead of having no smell?
Selected-source overview · Independent review pending. Read the evidence context.
That experience can be called parosmia: distortion of an odor that is present. It differs from complete loss of smell and is useful to describe specifically during assessment.[1]
Evidence behind this answer
- Smell Disorders
agency condition or prevention explanation · 2013
Relevant original source text read; no independent full evidence appraisal · Types, causes, flavor and clinical assessment
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
What if I smell something that other people cannot detect?
Selected-source overview · Independent review pending. Read the evidence context.
An odor perception without an outside source is called phantosmia. Report its pattern and other symptoms to a clinician; the term describes the experience rather than establishing a cause.[1]
Evidence behind this answer
- Smell Disorders
agency condition or prevention explanation · 2013
Relevant original source text read; no independent full evidence appraisal · Types, causes, flavor and clinical assessment
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Can food seem tasteless even when I can still detect sweetness?
Selected-source overview · Independent review pending. Read the evidence context.
Yes. Basic taste and food aroma are different parts of flavor. Reduced smell can make food seem bland while some taste qualities remain detectable.[2]
Evidence behind this answer
- Taste Disorders
agency condition or prevention explanation · 2013
Relevant original source text read; no independent full evidence appraisal · Taste and flavor; common chemical sense; causes; assessment and medicine caution
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does feeling chili heat or mint coolness show that my taste is normal?
Selected-source overview · Independent review pending. Read the evidence context.
No. Those sensations involve the common chemical sense. They are different from the taste qualities and aromas that contribute to flavor.[2]
Evidence behind this answer
- Taste Disorders
agency condition or prevention explanation · 2013
Relevant original source text read; no independent full evidence appraisal · Taste and flavor; common chemical sense; causes; assessment and medicine caution
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
How long should I wait before arranging a routine smell assessment?
Selected-source overview · Independent review pending. Read the evidence context.
The NHS advises a GP appointment if smell has not returned to normal in a few weeks. This routine timing should not be used to postpone assessment of an injury or other concerning illness.[3]
Evidence behind this answer
- Lost or changed sense of smell
agency condition or prevention explanation · Date not stated
Relevant original source text read; no independent full evidence appraisal · When to see a GP; recovery; safety
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does a post-viral smell change always resolve in a few weeks?
Selected-source overview · Independent review pending. Read the evidence context.
No. Recovery may take weeks or months, and some people have persistent changes. Assessment can identify treatable nasal problems and help manage the consequences.[3]
Evidence behind this answer
- Lost or changed sense of smell
agency condition or prevention explanation · Date not stated
Relevant original source text read; no independent full evidence appraisal · When to see a GP; recovery; safety
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Is smell training guaranteed to work after COVID-19?
Selected-source overview · Independent review pending. Read the evidence context.
No. In the 2025 placebo-controlled trial, objective smell improvement did not differ after 12 weeks. The trial studied a particular selected adult group and had dropouts; one result cannot settle all rehabilitation approaches.[5]
Evidence behind this answer
- Effect of Olfactory Training in COVID-19 Related Olfactory Dysfunction—A Placebo-Controlled Trial
randomized controlled trial · 2025
Relevant original source text read; no independent full evidence appraisal · Abstract; methods; participant flow and objective TDI outcome
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Why might smell training still be discussed when one trial was negative?
Selected-source overview · Independent review pending. Read the evidence context.
Recommendations consider a broader, earlier evidence base, while an individual trial tests a defined population and method. The 2022 consensus favored training, but a recommendation is not a promise of individual benefit.[4]
Evidence behind this answer
- Ask the Experts: An International Consensus on Managing Post-Infectious Olfactory Dysfunction Including COVID-19
expert consensus review · 2022
Relevant original source text read; no independent full evidence appraisal · Management of PIOD–Olfactory Training; recommendations; conclusion
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does the evidence support taking oral steroids for persistent smell loss after COVID-19?
Selected-source overview · Independent review pending. Read the evidence context.
The placebo-controlled prednisolone trial did not show benefit for its studied post-COVID group. It does not justify self-starting oral steroids or replacing assessment of the cause.[6]
Evidence behind this answer
- Prednisolone does not improve olfactory function after COVID-19: a randomized, double-blind, placebo-controlled trial
randomized controlled trial · 2022
Relevant original trial text and the original published correction read; only qualitative corrected finding used · Abstract, methods and primary outcome; read together with2023 correction atPMC9933010
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does a review with an old search date include the newest smell-loss trials?
Selected-source overview · Independent review pending. Read the evidence context.
No. The cited Cochrane review searched through October 2021. Later trials need separate appraisal; their publication dates should not be confused with the review’s search date.[7]
Evidence behind this answer
- Interventions for the treatment of persistent post-COVID-19 olfactory dysfunction
systematic review · 2022
Original complete public abstract and plain-language summary read; full review methods and forest plots not independently appraised · Original Cochrane plain-language summary and abstract; search through20October2021; two trials30participants
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Smell training is a rehabilitation approach, with limits
Smell training involves repeated practice with a set of odors over time. A 2022 expert consensus recommended it as a first-line option for post-infectious smell dysfunction. That recommendation concerns an approach to discuss in the relevant clinical context; it does not establish that every smell change has an infectious cause or that training guarantees recovery.[4]
A newer placebo-controlled trial found no objective advantage
A 2025 single-center trial randomized 65 adults with smell dysfunction lasting more than 12 weeks after confirmed COVID-19 to odor training or odor-free placebo oils for 12 weeks. Sixteen participants dropped out. Objective smell-test improvement did not differ between groups. This specific study limits confidence in a guaranteed benefit; it does not settle every training method, duration or non-COVID cause.[5]
Oral steroid evidence is specific to the studied problem
In a 2022 trial, 115 adults with persistent smell dysfunction four to 12 weeks after confirmed COVID-19 received prednisolone or placebo; both groups also undertook smell training. Prednisolone did not improve the primary smell-test outcome at 12 weeks. A published correction amended numerical results, so uncorrected effect estimates should not be repeated. This is not a trial of every nasal treatment or cause of smell loss.[6]
Older reviews and newer trials answer different questions
The Cochrane review included only 30 participants across two treatment comparisons and judged the evidence very uncertain. The review’s search date matters. Combining it informally with later trials would not produce a new systematic review or identify a treatment that suits an individual.[7]
References
- Smell Disorders
Agency condition or prevention explanation
National Institute on Deafness and Other Communication Disorders · Content/publication date: 2013
Accessed: 2026-10-20 UTC · Relevant original source text read; no independent full evidence appraisal
Cited sections: Types, causes, flavor and clinical assessment - Taste Disorders
Agency condition or prevention explanation
National Institute on Deafness and Other Communication Disorders · Content/publication date: 2013
Accessed: 2026-10-20 UTC · Relevant original source text read; no independent full evidence appraisal
Cited sections: Taste and flavor; common chemical sense; causes; assessment and medicine caution - Lost or changed sense of smell
Agency condition or prevention explanation
NHS · Content/publication date: not stated
Accessed: 2026-10-20 UTC · Relevant original source text read; no independent full evidence appraisal
Cited sections: When to see a GP; recovery; safety - Ask the Experts: An International Consensus on Managing Post-Infectious Olfactory Dysfunction Including COVID-19
Expert consensus review
Sohaib Mallick, Javier Ash, Alfred Addison and Carl Philpott · Content/publication date: 2022
Accessed: 2026-10-20 UTC · Relevant original source text read; no independent full evidence appraisal
Cited sections: Management of PIOD–Olfactory Training; recommendations; conclusion - Effect of Olfactory Training in COVID-19 Related Olfactory Dysfunction—A Placebo-Controlled Trial
Randomized controlled trial
Ditte Gertz Mogensen and colleagues · Content/publication date: 2025
Accessed: 2026-10-20 UTC · Relevant original source text read; no independent full evidence appraisal
Cited sections: Abstract; methods; participant flow and objective TDI outcome - Prednisolone does not improve olfactory function after COVID-19: a randomized, double-blind, placebo-controlled trial
Randomized controlled trial
Emma J. A. Schepens and colleagues · Content/publication date: 2022
Accessed: 2026-10-20 UTC · Relevant original trial text and the original published correction read; only qualitative corrected finding used
Cited sections: Abstract, methods and primary outcome; read together with2023 correction atPMC9933010 - Interventions for the treatment of persistent post-COVID-19 olfactory dysfunction
Systematic review
Lucy O’Byrne and colleagues / Cochrane · Content/publication date: 2022
Accessed: 2026-10-20 UTC · Original complete public abstract and plain-language summary read; full review methods and forest plots not independently appraised
Cited sections: Original Cochrane plain-language summary and abstract; search through20October2021; two trials30participants
Scope & review
- Population
- People with changed smell, taste or food flavor; adult post-COVID trial populations distinguished
- Exposure or intervention
- Symptom description, clinical assessment, practical consequences and selected smell rehabilitation evidence
- Comparison
- Odor training versus odor-free placebo; prednisolone versus placebo with training in both groups; older small treatment comparisons
- Outcomes
- Meaning of sensory changes, objective smell-test outcomes, uncertainty and appropriate follow-up
- Timeframe
- Source-specific publication, update and search dates remain separate; checked 2026-10-20 UTC
- Jurisdiction
- US agency explanations; UK NHS and expert review; Danish and Dutch adult trials. Local referral and care arrangements differ.
Targeted original-source reading and comparison with current guide bodies, tables and FAQs. Claim-linked selected recommendations and study findings are educational synthesis, not a systematic search, independent evidence grade or qualified clinical review.
Sources checked on their individual access dates. Selected sources were checked; ongoing surveillance and qualified review have separate statuses on the coverage page.
Revision history
- 2026-10-20 UTC: New symptom guide drafted after source verification, existing-scope comparison and cumulative attribution audit; qualified review pending.
What this article still leaves open
- Which cause and testing pathway best fit the individual history?
- Which training methods and durations help particular groups beyond the selected trials?
- No universal recovery deadline, medication regimen or independent systematic evidence grade is supplied.
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