Post-COVID smell loss

Smell loss after COVID, and parosmia.

Losing your sense of smell after COVID is common. So is the stage that often comes later, where coffee smells like garbage and meat smells like it has gone off. That one is called parosmia. Below is what the research says about both, and what people have found helps while they wait it out. This is educational information, not medical advice.

What happened to your sense of smell

More people lose smell with COVID than say they do. When researchers tested smell directly rather than asking about it, about 77 percent of COVID patients came out with measurable loss. Only 44 percent reported it themselves.

Source: Monell Chemical Senses Center, reporting Hannum et al. in Chemical Senses. Better Measures Reveal More COVID-19 Smell Loss

The virus does not seem to attack the smell nerves directly. A team at Harvard worked out which cells in the nose carry the receptor the virus uses to get in, and found it on the support cells that surround and feed the olfactory nerve cells, and on some stem cells and blood vessel cells. The olfactory sensory neurons themselves did not carry it. Their reading was that COVID disrupts smell by damaging the support system rather than the neurons, so the neurons may not have to be rebuilt from scratch. They also said that more data is needed before anyone treats that as settled.

Source: Brann et al., Science Advances, 2020, summarized by Harvard. How to understand COVID-19-related loss of smell

Either way, tissue in your nose was damaged and is now repairing itself. That takes months, and it rarely goes in a straight line.

How long recovery usually takes

Most people get it back. A 2022 meta-analysis in The BMJ pooled 18 studies covering 3,699 patients and found smell recovery reported by 74.1 percent at 30 days, 85.8 percent at 60 days, 90 percent at 90 days and 95.7 percent at 180 days.

The same paper put the share who go on to long lasting smell dysfunction at roughly 5.6 percent, and noted that this could be low, since nearly every study in it relied on people reporting their own smell rather than having it measured.

Source: Tan et al., The BMJ, 2022. Prognosis and persistence of smell and taste dysfunction in patients with covid-19

If you are six months or a year out and still not right, you are in the smaller group. It is a well documented group, and the patient organizations listed further down exist largely because of it.

Recovery tends to be patchy. Strong, simple smells usually come back before subtle ones, and it is normal for one week to be better than the next. The NHS advises seeing a doctor if your sense of smell has not gone back to normal within a few weeks.

Source: NHS. Lost or changed sense of smell

Parosmia, when everything smells wrong

The NIDCD, part of the National Institutes of Health, defines parosmia as a change in the normal perception of odors, such as when the smell of something familiar is distorted, or when something that normally smells pleasant now smells foul.

Source: NIDCD, National Institutes of Health. Smell Disorders

That is the clinical wording. People describe it more bluntly. Coffee smells like garbage, meat smells like it is rotting, and the kitchen becomes hard to walk into. Monell’s researchers report the same examples, coffee smelling like garbage or rotting meat.

Source: Monell Chemical Senses Center. Distinct Differences Exist Between Sense of Smell Distortions Associated With COVID-19

When it starts, and what sets it off

Parosmia usually shows up months after the smell loss rather than alongside it. Researchers at the University of Reading surveyed 727 people with post-COVID parosmia and found distortions started a median of 2.8 months after the original loss, with a mean of 4.4 months. Ninety five percent started within six months. Smell coming back and then turning strange is the usual sequence.

Coffee, meat and onion were the items most often distorted in that survey, and the ones people rated worst. Chocolate, egg, garlic and citrus came up repeatedly as well. Across the survey, 84 percent of distorted items were rated unpleasant or gag inducing, against 16 percent rated pleasant or neutral.

Source: Parker et al., Foods, 2022, University of Reading. Emerging Pattern of Post-COVID-19 Parosmia and Its Effect on Food Perception

Parosmia and recovery

There is evidence that parosmia goes along with recovery rather than against it. In a study of 246 people with smell loss following infection, the presence of parosmia at the first appointment was one of two predictors of a clinically relevant recovery after smell training. Low smell function at the start was the other.

Source: Liu et al., The Laryngoscope, 2021. Parosmia is Associated with Relevant Olfactory Recovery After Olfactory Training

Monell surveyed more than 2,100 people with smell disorders and found parosmia commonly settled within three to six months, with people reporting improvement over time. Those are group figures. Individual courses vary a lot, and some people have distortions for a good deal longer than six months.

Source: Monell Chemical Senses Center. Distinct Differences Exist Between Sense of Smell Distortions Associated With COVID-19

Getting through meals

Nothing available at the moment turns parosmia off, so most of the practical advice is about working around it. SmellTaste, the UK charity that used to be Fifth Sense, publishes a sheet developed with the Smell and Taste Clinic at the James Paget Hospital. Their suggestions:

Work out your triggers and leave them alone for a while. Coffee, dark chocolate, wine, egg, onion, roasted and fried foods and citrus come up most often.
Try plainer, cooler food. White chocolate, cheese, fruit, miso, salad, vegetables, pasta and sushi are often easier than a hot cooked meal.
Mask what you can. A strong flavor that does not distort for you, cinnamon or chili oil or peppercorn sauce, can carry a whole plate.
A nose clip while eating helps some people. It closes off the route the distortion arrives by.
Unscented toiletries and cleaning products. Fewer things at home to run into.

Source: SmellTaste, formerly Fifth Sense. Parosmia and Phantosmia and the Coping with Parosmia and Phantosmia information sheet

No pill, supplement, nasal spray or injection currently has solid evidence behind it for parosmia. A clinician is the right person to ask before spending money on anything sold for it.

If you are eating much less than you used to, or cutting out whole categories of food, it is worth telling your doctor. Weight and nutrition are the part of parosmia most likely to need attention.

Phantosmia, the smells that are not there

Phantosmia is the NIDCD term for the sensation of an odor that is not there. People describe smoke, burning or chemicals, with nothing in the room to account for it.

It is less common than parosmia and behaves differently. In Monell’s survey of more than 2,100 people with smell disorders, 19 percent had parosmia only, 11 percent had phantosmia only, and 16 percent had both. Phantom smells were more often set off by a place, a time of day, stress or a memory than by a particular food, and they stayed more stable over time instead of easing the way parosmia tended to.

The NIDCD lists conditions affecting the nervous system among the causes of smell disorders, along with head injury, growths in the nasal cavities and a range of medications. Phantom smells are worth mentioning at a medical appointment for that reason.

Sources: NIDCD, Smell Disorders and Monell Chemical Senses Center

What helps

Smell training

Smell training has more evidence behind it than anything else available for acquired smell loss. A 2017 meta-analysis pooled 13 studies covering roughly a thousand patients and found a significant positive effect on odor identification, odor discrimination and overall smell score, with a smaller effect on detection threshold. Longer training worked better than shorter training.

Source: Sorokowska, Drechsler, Karwowski and Hummel, Rhinology, 2017. Effects of olfactory training: a meta-analysis

The protocol is four scents, 20 to 30 seconds each, twice a day, which makes it cheap and low risk. It does not work for everyone. Our smell training page has the full method and where to get a kit.

How to do smell training

Seeing a clinician

The NIDCD’s advice is to talk with your doctor if you are experiencing a smell disorder. The specialist for smell problems is an otolaryngologist, usually called an ENT.

Situations where people are generally advised to get checked, drawn from the NHS guidance and the causes the NIDCD lists: smell has not returned to normal after a few weeks, the loss started without a cold, flu or COVID, it followed a head injury, there is ongoing nasal blockage, polyps or facial pain, a medication could be involved, or the change in smell arrived with other new symptoms. An ENT can check for causes that have their own treatment, which smell training would not address.

Sources: NIDCD, Smell Disorders and NHS, Lost or changed sense of smell

Safety while your nose is unreliable

Smoke alarms and a natural gas detector matter more than usual while your nose is not working. Do not rely on the sniff test for food. Dates are a starting point, but lean on time and temperature: refrigerate promptly, date-mark leftovers, and throw out anything borderline. If someone else is around, ask them to check anything you are unsure about. Our guide to living safely with anosmia covers the equipment and habits in more detail.

You are not alone

Somewhere to go next.

Smell loss is hard to explain to people who have not had it, and that comes up in almost every message we get.

The Stories wall collects first person accounts, including one about smell that comes and goes after COVID. On the Resources page there are patient organizations, support groups, clinics and suppliers of smell training kits. The FAQ covers the questions we get asked most often.

If you have been through this, your account would help the next person who lands on this page. A few paragraphs is enough, and you can stay anonymous. Share your story.

Read the stories

Go to Resources

Everything on this page is educational and is not medical advice. Anosmia Awareness is a patient led nonprofit and not a clinic. We do not diagnose, treat or recommend treatment, and we do not conduct research ourselves. Please talk to a doctor about your own situation.