Smelling smoke, burning, or something rotten when nothing is there is called phantosmia, and it is a recognized after-effect of COVID. The virus and the body’s immune response injure the smell system, and its repair doesn’t always go smoothly. For most people the phantom smells are temporary, though they can take months to settle.
Phantom Smells Versus Distorted Smells
Two different problems get confused. Distorted smell means a real smell comes through wrong, such as coffee smelling like garbage. With phantom smells there is no source at all, and few people with them can point to anything that sets them off.1Monell Chemical Senses Center. Distinct Differences Exist Between Sense of Smell Distortions Associated With COVID-19, Monell Center Researchers Find Among people with long-lasting smell problems after COVID, many had both at once.2PubMed Central. Impairment of quality of life due to COVID-19-induced long-term olfactory dysfunction Viral infections lead to distorted smell more often, while head injuries lead to phantom smells more often.3Monell Chemical Senses Center. Distinct Differences Exist Between Sense of Smell Distortions Associated With COVID-19, Monell Center Researchers Find
In daily life, the first clue is whether the bad smell shows up around coffee, meat, onions, or a certain soap. That points to distorted smell, because a real odor is being scrambled on its way to your brain. If the smell arrives in a clean, empty room with nothing cooking or burning, that fits a phantom smell, since nothing in the air is being altered. The trigger test is a clue, not a verdict.
Other people can serve as a check. When you smell smoke or something rotten, ask someone nearby whether they smell it too. If they do, look for a real source such as a pan, a drain, or a gas leak. If you’re the only one and nothing around you could explain it, a phantom smell becomes more likely, though one person’s sniff is not proof either way.
People most often describe phantom smells as smoke, burning, chemicals, or rotting odors. They are usually unpleasant rather than pleasant, and an episode can last seconds or linger for hours.
How Common Phantom Smells Are After COVID
About 37% of people with smell problems after COVID reported phantom smells.4PubMed Central. Phantom smells: a prevalent COVID-19 symptom that progressively sets in In one group followed for three years, about 43% had experienced them.5PubMed Central. Three-year assessment of cognitive and olfactory disturbances among COVID-19 convalescent patients grouped by olfactory hallucination status in Armenia: A qualitative and quantitative study The problem has also been reported in otherwise healthy young adults with no other conditions,6Rhinology Online. Characterization, treatment modalities, and self-perceived improvement of post-COVID-19 phantosmia: a case series of eleven patients and phantom smells were most common among people in their 40s.7Monell Chemical Senses Center. Distinct Differences Exist Between Sense of Smell Distortions Associated With COVID-19, Monell Center Researchers Find
These percentages describe people who already had smell trouble, not everyone who caught COVID. Most people who had COVID and got their smell back quickly never experience phantom smells at all, so the odds overall are much lower than those numbers suggest.
Many people never connect the smell to COVID at first. Phantom smells can start weeks or months after the infection, once the cold-like symptoms are long gone, so people often blame stress, mold, or a problem at home.
What Causes Phantom Smells After COVID
The leading explanation starts with inflammation that outlasts the virus. COVID triggers immune cells and inflammatory chemicals in the lining of the nose that senses smell,8PubMed Central. Mechanisms of COVID-19-associated olfactory dysfunction so those chemicals are raised in that tissue during infection.9PubMed. Proinflammatory Cytokines in the Olfactory Mucosa Result in COVID-19 Induced Anosmia The immune response is meant to clear the virus, but the chemicals it releases can also harm the delicate smell-sensing cells.
In people with long-lasting smell loss, immune inflammation continued in that tissue long after the virus was gone.10PubMed Central. Persistent post–COVID-19 smell loss is associated with immune cell infiltration and altered gene expression in olfactory epithelium That ongoing inflammation went along with fewer smell-sensing nerve cells.11PubMed Central. Persistent post–COVID-19 smell loss is associated with immune cell infiltration and altered gene expression in olfactory epithelium In some people with long-lasting loss, traces of the virus itself remained in the smell tissue.12PubMed Central. COVID-19-related anosmia is associated with viral persistence and inflammation in human olfactory epithelium and brain infection in hamsters
The second explanation is repair that rewires imperfectly. Smell nerves in the nose can regrow after damage. But regrowing nerves don’t always reconnect to the same spots in the brain’s smell center, so signals get scrambled.13ENTtoday. The Latest on Olfactory Dysfunction and COVID-19 Brain areas that process smell also show weaker links in people with smell distortion.14PubMed Central. Functional connectivity patterns in parosmia A damaged or irritated smell nerve can fire without any odor molecule touching it, and the brain may read that firing as a real smell.
How Long Phantosmia Lasts
Phantom smells can appear months after COVID, even after smell seemed fully back.15PubMed Central. Long-Term Olfactory Dysfunction in COVID-19 Patients: A Systematic Review In one trial, they affected about 7% of patients at 3 months and none at 12 months.16PubMed Central. Therapeutic effects of olfactory training and systemic vitamin A in patients with COVID-19-related olfactory dysfunction: a double-blinded randomized controlled clinical trial That comes from one group and is not a promise for any one person. Phantom smells also tend to be steadier over time than distorted smell, which more often improves.17Monell Chemical Senses Center. Distinct Differences Exist Between Sense of Smell Distortions Associated With COVID-19, Monell Center Researchers Find
Phantom smells may also say something about your overall sense of smell. Having them early on was linked to about 2.5 times the chance of smell problems still present a year later.18PubMed Central. Phantosmia May Predict Long-Term Measurable Olfactory Dysfunction After COVID-19 In that group, smell loss affected 75% of people at first and about 30% still had it after a year.19PubMed Central. Phantosmia May Predict Long-Term Measurable Olfactory Dysfunction After COVID-19 That is a tendency in a group, not a prediction for you, and most people in that group had improved.
A simple log helps you see progress. Write down the date and time of each episode, what the smell was like, how strong it was, and how long it lasted; a phone note is enough. Compare month to month rather than day to day, looking for fewer or shorter episodes as a sign of healing. A doctor will find the record useful, since memory is unreliable.
What Can Help
Smell training means sniffing a few strong scents twice a day for months to retrain the system. Choose four distinct scents, commonly rose, lemon, clove, and eucalyptus, using essential oils or pure spices kept in small jars. Hold one jar under your nose and sniff gently for about 20 seconds, then rest briefly before the next scent, and repeat the set morning and evening. While sniffing, try to picture the real smell, such as a lemon being sliced, because the mental effort is part of how the training works. Keep going for at least three months.
In one program, phantom smells didn’t clearly decrease, with some people gaining them and others losing them.20PubMed Central. Olfactory Training in Post-COVID-19 Persistent Olfactory Disorders: Value Normalization for Threshold but Not Identification So try smell training for your overall sense of smell, but don’t expect it to stop phantom smells directly. If it seems to make them worse for you, it is reasonable to pause and discuss it with a doctor.
Some people find that saline rinses or briefly sniffing a strong familiar scent interrupts an episode. Because phantom smells can mimic smoke or gas, keep your smoke and gas detectors working so you can trust real alarms, and ask others to confirm any smell of gas or burning.
A nerve-block injection in the neck has improved smell in small groups of people with long COVID.21PubMed Central. Efficacy of Stellate Ganglion Block in Treating Long-Term COVID-19-Related Olfactory and Gustatory Dysfunction: A Case Series That evidence comes from case reports, so it is not established treatment.22Pain Medicine Case Reports. Alleviation of COVID-19 Parosmia with Stellate Ganglion Block: A Case Report Ask a smell specialist before pursuing it.
The Emotional Toll
People with post-COVID smell problems report lower quality of life, especially around food and pleasure.23PubMed Central. Impact of post-COVID-19 olfactory disorders on quality of life, hedonic experiences and psychiatric dimensions in general population Phantom smells are linked to more depressive symptoms.24PubMed Central. Parosmia Is Positively Associated With Problematic Drinking, as Is Phantosmia With Depressive Symptoms
Food is the most common casualty, since much of what we call taste is smell. Some people eat less or stick to plain foods, and notice weight change as a result.
A bad smell that comes and goes with no warning is wearing, because you can never relax or be sure when it will return. It can disturb sleep, raise stress, and make people avoid meals or social events.
Support groups for people with smell loss exist online and in some areas in person, and hearing from others who understand can reduce isolation. If low mood, hopelessness, or anxiety lasts for weeks, mention it to a doctor rather than waiting it out alone. Depressive symptoms can be treated in their own right.
When to See a Doctor
Phantom smells can also come from seizures, migraines, or recovery after a head injury.25ENTtoday. The Latest on Olfactory Dysfunction and COVID-19 A doctor may ask about recent COVID and migraines, look inside the nose with a small camera, order a brain scan, or test brain activity for seizures.26UT MD Anderson. Phantosmia: 8 things to know about olfactory hallucinations See a doctor if phantom smells come with headaches, confusion, or staring spells, or started without a clear COVID link.
A phantom smell in only one nostril or on one side can suggest a local cause that needs examination. Smells that come with jerking, staring, confusion, or lost awareness may be a type of seizure and should be checked promptly. Episodes that steadily grow more frequent or intense, instead of fading, do not fit the usual pattern of recovery.
Before the appointment, write down roughly when you had COVID and when the first phantom smell appeared, since the gap helps the doctor judge the cause. Describe what the smell is like, how often it comes, how long it lasts, and anything that sets it off or relieves it. Bring a list of your medicines and mention any past head injury or migraines, because these can cause phantom smells too. Ask whether an ear, nose, and throat specialist is appropriate, since they can look inside the nose and check the smell tissue.