Mind & Body · Monday, 31 August 2026

01 Briefing what happened

You have about 400 kinds of smell receptor, and not one of them is the coffee one

Mind & Body 1 min 57 sources

A smell is not a signal from one sensor. It is a pattern across a few hundred of them, none of which means anything on its own - which is why you can know a smell at once and still not be able to name it.

391

working smell receptor genes in human DNA

a mouse carries about 1,100 and a dog 779 to 807 [1][2][8]

60%

of the human smell receptor gene family is broken by mutations

not the same genes in each person, so no two noses run the same set [7]

under 50%

of common everyday smells that people can correctly name

the same people name over 90% of familiar objects by sight [6]

22%

of people have some loss of smell, and about 5% have none at all

more than the reported rates of profound deafness or blindness [12]

The lead story — what happened

Smell starts in a patch of tissue in the roof of your nose. Human DNA carries 391 working smell receptor genes, and that is the whole toolkit. [1]
There is no receptor for coffee. There is no receptor for lemon, or rain, or your grandmother's kitchen. Each one responds roughly, to many different molecules. [1]
The standard account is a pattern. A molecule switches on some receptors and not others, and which set lights up is the smell. That is how a few hundred parts cover far more than a few hundred smells. [1]
Each smell nerve cell picks exactly one receptor gene and silences all the others. In mice that is one out of more than 1,000, and a protein called TRIM66 does the silencing. [4]
Every cell that picked the same receptor sends its wire to the same bundle in the smell bulb, the first stop in the brain. A mouse bulb holds a median of 2,851 bundles, about 2.5 for each intact receptor gene. [9]
Camillo Golgi described those bundles in 1875. Nobody had counted them completely until this work; every earlier figure was an estimate. [9]
The receptor genes themselves were found in 1991 by Linda Buck and Richard Axel, who shared the 2004 Nobel prize in medicine for it. [5]
Two papers in the journal Cell in May 2026 redrew where the receptors sit. Each one occupies a set position along the roof of the mouse nose, rather than a broad zone picked at random. [2][3]
The two maps line up. Where a receptor sits in the nose predicts where its wires land in the brain, through one shared set of genes. [2]
The pattern account is under pressure from the other side too. In 2025 chemists found human receptors tuned tightly to single molecules: the cork taint in wine, the pepper note, grapefruit, ambergris. [1]
One human receptor, OR52E8, answers to a single acid in armpit sweat. Natural variants of it respond differently from one person to the next. [54]
About 60% of the human smell receptor gene family is broken by mutations, and not the same genes in each person. [7]
So two people in one room are not running the same equipment. Where you live explains 17 to 20% of the difference in how sensitive people are to odours, measured in 1,046 people across 19 places. [16]
What people find pleasant is more shared than that. In 909 people across 16 regions, region explained under 10% of the variation, and intensity varied more than pleasantness. [17]
The pattern arrives with no name attached. People correctly name under half of common everyday smells, and over 90% of familiar objects they can see. [6]
Smell takes the shortest route to feeling of any sense: only two nerve-cell junctions separate the nose from the brain's emotion circuits. [57]
It is also the sense health systems skip. About 22% of people have some loss of smell and about 5% have none at all, and no country's public health plan covers it. [12][13]

Who is involved

Linda Buck and Richard Axel

the two biologists who found the smell receptor genes in 1991; they shared the 2004 Nobel prize in medicine for it [5]
Carl Philpott and Thomas Hummel

smell researchers at the University of East Anglia in the UK and the Technical University of Dresden in Germany; they are pushing to get smell into public health policy [12]
Roger Emter and Andreas Natsch

the chemists who matched single human receptors to the cork taint in wine, to grapefruit and to ambergris [1]
Osarenoma Olomu

an ear, nose and throat doctor at Mayo Clinic in Jacksonville in the US; running blood-platelet injections for people who have lost their smell [18]

What is pushing on this

The textbook under strain Building↑

two Cell papers overturned the zone map, and a 2025 study found tightly tuned receptors [2][3][1]

Smell tests pushed as an early warning Building↑

Parkinson's risk screens run in 1,472 and in 1,044 people [26][27]

The gap between testing and treating High→

screens have run in over 2,500 people while the main treatment is still sniffing four scents [26][27][24]

Smell missing from health policy High→

no country's public health agenda covers it, though about 22% of people are affected [12]

How it unfolded

1875 Camillo Golgi describes the bundles in the smell bulb where the nerve wires gather [9]
1991 Buck and Axel find the smell receptor genes [5]
2004 they share the Nobel prize in medicine for the discovery [5]
2014 a paper in Science puts the number of smells humans can tell apart above one trillion [11]
2020-2022 COVID makes smell loss a mass experience and turns attention on the support cells the virus infects [18]
May 2026 two papers in Cell overturn the zone map of where receptors sit in the nose [2][3]

Where this points

Watch whether the tightly tuned receptors found in 2025 turn out to be the exception or the rule; if many receptors are that specific, the map from molecule to smell gets far easier to build. [1][5]

The rest of the day

40 more stories on this beat.

Each with its own sources. None of these is a link to the story above.

02
Two-thirds had lost smell without knowing

In a US study of 3,525 people, 66% of the 1,563 previously infected who reported no change in smell scored as having reduced smell on a 40-odour test, 8.2% of them severely. Among those who did report a change, 79.8% did. [19]

Why it matters — How common smell loss is depends on whether you test people or ask them.
03
COVID smell loss runs for years

A review of 21 studies covering more than 4,000 people found losses lasting from several months to over two years, with distorted and phantom smells appearing during recovery. [20]

Why it matters — The recovery is not a return to normal so much as a slow, strange rebuild.
04
A quarter still affected a year on

Between 26.5% and 46% of people who had COVID still had smell loss one year after infection, falling to 8.3% at two years. [21]

Why it matters — Most people do recover, and the tail is long enough to be a public health problem.
05
Four bottles, twice a day, for months

The standard treatment, olfactory training, is smelling four different scents for 10 to 20 seconds each, twice a day, for at least three months. [24]

Why it matters — It is the main thing medicine has to offer for a sense that a fifth of people have lost some of.
06
The sniffing works; the add-ons work harder

A meta-analysis of eight randomised trials found training effective, with the largest gain when it was combined with the supplement PEA-luteolin, and higher recovery rates for combinations generally. [23]

Why it matters — The sniffing is the part everyone can do and the smaller part of the effect.
07
Platelet injections show a real signal

Two 2025 meta-analyses, one of four trials in 198 people and one of seven studies in 789, found injections of the patient's own blood platelets beat placebo at 1, 3 and 12 months. Mayo Clinic reports 87% of its patients clinically improved a year on. [21][22][18]

Why it matters — The first treatment in decades to be added to a hospital protocol for smell loss.
08
Nasal polyps take smell first

Between 67% and 78% of people with chronic sinus inflammation have impaired smell, and the presence of polyps is among the strongest factors. [25]

Why it matters — The commonest cause of lost smell is not a virus, it is a blocked and inflamed nose.
09
A five-question smell test for Parkinson's

A shortened five-item smell test was run in 1,472 people over 60 with no Parkinson's diagnosis. Scores fell with age, were worse in men, and tracked with a REM sleep disorder screen. [26]

Why it matters — Smell loss can precede the tremor by years, which is why a cheap test is attractive.
10
A quarter of over-50s screened had unexplained loss

Of 1,044 people screened with a rapid smell test in Iran, 25% of those over 50 had smell loss with no identified cause, against under 10% of younger people. [27]

Why it matters — The screening pool is large, and most of those people will never develop Parkinson's.
11
Parkinson's changes which smells are pleasant

In 94 people, only a detailed perceptual profile separated Parkinson's from other smell loss, telling the groups apart with 88% accuracy, rising to 94% when age and sex were matched. Between 75% and 90% of people with Parkinson's have smell loss. [28]

Why it matters — The finding is not that smell fades but that the same lemon stops being enjoyable.
12
In Parkinson's the loss is brain-wide

Olfactory loss in Parkinson's reflects widespread degeneration across the movement and rear cortical networks, not damage confined to the nose. [29]

Why it matters — It explains why smell tracks with later thinking problems rather than only with the nose.
13
Odour naming tested for early Alzheimer's

A review of olfactory testing in mild cognitive impairment found identification and discrimination the domains most impaired in Alzheimer's, and called for tests adapted to different cultures. [30]

Why it matters — A test built around Western smells fails everywhere else, and most such tests are.
14
Poor smell tracked heart disease, then stopped

In 5,142 older US adults followed 9.6 years, poor smell carried about twice the risk of coronary heart disease at year two, falling to no measurable difference by year 9.6. [31]

Why it matters — A signal that decays like that usually means something already under way, not a cause.
15
Children's smell disorders go unlooked for

Smell disorders affect about 22% of people overall, but only about 2% of patients at specialist smell clinics are under 18. Age-specific normal ranges for children's tests barely exist. [32]

Why it matters — A child who cannot smell gas or spoiled food has the same safety problem as an adult.
16
Cage fighters scored lower on smell

Fourteen mixed martial arts fighters scored lower than 14 matched controls on the 40-item smell identification test, a statistically significant gap, with no difference in taste. [33]

Why it matters — The nerve fibres running to the brain pass through a thin plate of bone, and a blow shears them.
17
Smell identification fell after menopause

In 80 women, those between six and ten years past menopause were far less likely to score well on odour identification than women of reproductive age. [34]

Why it matters — One of the few studies looking at smell against a hormonal timeline rather than age alone.
18
A questionnaire as a cheap screen

In 228 adults, 58.3% of those over 50 had reduced smell against 19.8% of the younger group. A questionnaire correlated with formal testing, which costs around $30 a go. [35]

Why it matters — The gap between what testing costs and what a clinic will pay is why nobody is tested.
19
An immune signal ages the nose

In mice, the inflammatory signal IL-17a builds up in ageing smell tissue and blocks its renewal. Blocking IL-17a restored nerve cell regeneration and reversed the tissue change. [36]

Why it matters — It reframes age-related smell loss as inflammation rather than simple wear.
20
A virus can leave bone behind

In mice, a virus destroyed the smell lining, immune cells moved in and stayed, and bone formed where sensory tissue had been. The smell loss was long-term. [37]

Why it matters — A tissue that normally rebuilds itself can be replaced by something that cannot smell.
21
Mucus glands become emergency stem cells

Glands beneath the smell lining that normally only produce mucus were shown to generate replacement support cells, but only after severe damage. [38]

Why it matters — A reserve nobody knew was there, held back until the usual repair route fails.
22
Some stem cells sit poised

Single-cell profiling of olfactory stem cells found a resting group already primed for activation, with the genetic switches open around genes not yet switched on. [39]

Why it matters — It shows the tissue keeps a set of cells ready rather than starting from scratch.
23
Immature nerve cells do their own job

Silencing the immature smell neurons in healthy mice impaired their ability to detect an odour, but not their ability to tell two odours apart. [40]

Why it matters — The half-built cells were assumed to be spare parts; they are a separate input stream.
24
The nose's bacteria are in the story

A review links shifts in the nasal microbiome to chronic sinusitis, allergic rhinitis and post-viral smell loss, while stating the evidence is largely indirect. [41]

Why it matters — A live hypothesis that has not yet shown which way the arrow points.
25
What makes a scent unlock a memory

In 106 people, 77% recognised an odour they had met one to three days earlier, and 55% of those recognitions brought back the episode attached to it. Emotional strength predicted recognition best. [42]

Why it matters — Recognising a smell and remembering what it belongs to are two separate steps.
26
Smell is a poor landmark

A review of 24 studies found people worse at remembering places by smell than by sight, by a moderate margin. [43]

Why it matters — The sense that binds hardest to feeling is one of the weakest at telling you where you are.
27
A matching smell speeds visual search

In 22 people, smelling lemon while hunting for a lemon among other fruit improved speed and accuracy. A mismatched smell hurt the strongest searchers most. [44]

Why it matters — The senses are not searching separately; one primes what the other is looking for.
28
Pleasant smells slowed breathing, music did not

A personally pleasant smell slowed breathing, deepened it, lowered heart rate and raised heart rate variability. A personally pleasant piece of music did none of that. [45]

Why it matters — Smell is sampled by breathing, so it can reach the calming machinery that sound cannot.
29
Aromatherapy trials look positive and noisy

A review of 21 studies in pregnancy found reduced nausea and anxiety. A review of 13 studies in new and expectant mothers found smaller effects on anxiety and sleep, with study-to-study disagreement of 88.7%. [46][47]

Why it matters — Disagreement that high means the average is describing very few of the studies in it.
30
An oil blend improved memory tasks

In 90 adults, a commercial essential oil blend and a sage control both beat no aroma on memory and executive function tasks, measured alongside blood oxygen in the brain. [48]

Why it matters — The control condition was another smell, which is the harder and rarer comparison.
31
Lavender's pain effect traced in mice

Inhaled lavender oil eased migraine-like pain in mice through a specific brain circuit running from the smell region to the hypothalamus. Blocking one receptor in that circuit abolished the effect. [49]

Why it matters — A mechanism means the effect can be tested rather than only reported.
32
Horses read human fear odour

Forty-three horses exposed to pads carrying human fear odour startled harder, gazed longer at novel objects and touched the person less than with joy or control pads. [50]

Why it matters — The chemical signal crosses species without either side intending to send it.
33
Mosquitoes pick people by chemistry

Across 42 women, pregnancy and the phase of the menstrual cycle changed how attractive they were to yellow fever mosquitoes. Twenty-seven volatile compounds were identified, one of them enough on its own to shift preference. [51]

Why it matters — Who gets bitten is a chemistry question, and it changes over weeks.
34
Fear in parents showed in offspring's noses

Mice trained to fear an odour grew more neurons carrying the matching receptor. So did their own offspring, who had never met the odour. [52]

Why it matters — The receptor mix a nose is built with is not fixed at birth by genes alone.
35
First structure for a greasy-smell receptor

A cryo-electron microscopy structure of a class II smell receptor showed an unusually large water-repelling pocket for fatty acid molecules and an unconventional way of switching on. [53]

Why it matters — Smell receptors have been almost unphotographable, which is why so few are matched to smells.
36
Two noses beat the better one

Pairs of people who discussed a smell and agreed a joint answer outperformed the better of the two individuals, on both discrimination and identification. [10]

Why it matters — Words fail for smell, and talking still helped, which nobody expected.
37
How perfume gets described in Chinese

An analysis of 29,372 reviews of 36 perfumes found descriptions leaning heavily on naming the source of a smell rather than on qualities of it. [55]

Why it matters — With no vocabulary for smells themselves, every language borrows the names of things.
38
Phantom smells have no validated test

Phantosmia is smelling something that is not there. Reliable validated tests for these distortions of smell quality do not currently exist. [56]

Why it matters — A symptom that cannot be measured cannot be counted, treated or trialled.
39
Dogs carry twice the gene set

Individual dogs carry 779 to 807 working smell receptor genes, against about 400 in humans and 1,100 in mice. A dog's nose is reported to hold 125 to 300 million receptors, against roughly 5 million in a person. [8][14]

Why it matters — The first number is how many kinds; the second is how many copies. The gap is the size of the array, not a different kind of sense.
40
Mountain mammals gave up smell genes

Across 27 mammal species living only above about 1,000 metres, the genes that had broken were heavily concentrated in smell receptors: about 23% fewer of them, and smell bulbs about 18% smaller than in lowland relatives. [15]

Why it matters — Thin air carries fewer odour molecules, and unused genes are not maintained.
41
Hunter-gatherers kept more of the set

Genomes from 50 Indigenous people of the Malay Peninsula showed fewer broken smell receptor genes than other populations. One farming group carried a distinct version of OR12D3, a gene also linked to insulin release. [7]

Why it matters — How people get their food appears to have shaped which smells they can still detect.

02 Lesson why it matters

The answer is in the pattern, not in any of the parts

When you cannot have one detector for every thing, you read many rough ones at once - and then nothing inside the system holds the answer by itself.

The twist

You can know a smell the instant you meet it and be unable to say what it is, because the identity was never stored anywhere as a name - only as which parts lit up.

How it works

Too many things to detect, too few parts to detect them with
So each part is made blunt: it answers to many things, roughly
Each thing then switches on its own particular set of parts
The set is the identity - the pattern is the answer, not the part
Which means no part of the system holds a label for anything

Where you've seen this

Writing

26 letters, none of which means anything, spell every word there is

Colour

three kinds of cone in the eye, and no cone anywhere for turquoise

The genetic code

four chemical letters, read three at a time, build every protein in you

Music

twelve notes, and the tune is which ones, in what order

The catch

It breaks wherever one thing matters enough to get a part of its own. Some smell receptors are tuned tightly to a single molecule, and losing that one part costs you that one thing and nothing else.

And the whole of it

Everyone is running a slightly different set of parts: about 60% of these genes are broken in most people, and not the same ones in each person. Nobody gets the view from another nose, and the pairs who talk a smell through still do better than either of them alone.

03 Truth what's really going on

What is really going on

Smell is being turned into a cheap early-warning test for brain disease faster than it is being understood, while the treatment for losing it is still four bottles and three months of sniffing.

Why it works on us — One enormous number does the work in each direction: a trillion smells, and a nearly 100% chance of neurodegenerative disease, are both repeated far more often than the studies underneath them.

Who gains

Makers and sellers of smell tests — Screening proposals for Parkinson's and Alzheimer's would put a test costing around $30 in front of far more people than the smell clinics currently see. [26][30][35]
Clinics offering blood-platelet injections — Mayo Clinic reports 87% of treated patients clinically improved a year on and has added the injections to its protocol, in a field where the only other option is months of sniffing. [18]
Essential oil sellers — Reviews reporting real if noisy benefits in pregnancy and in hospital wards are the citations the marketing rests on, and the reviews' own heterogeneity figures do not travel with them. [46][47]
The fragrance and flavour industry — Matching single receptors to signature smells such as cork taint, grapefruit and ambergris turns odour design from trial and error into a targeting problem. [1]
Researchers on neurodegeneration — Smell offers a cheap, non-invasive marker that moves years before the tremor does, which is exactly what a prevention trial needs to recruit on. [26][28]

Who pays

People who have lost smell and were never asked about it — About 22% of people have some loss, and no country's public health agenda covers smell at all. [12]
Children with smell disorders — Only about 2% of specialist smell clinic patients are under 18, and age-specific normal ranges for the tests barely exist. [32]
Anyone handed a screening result with nothing behind it — The main treatment is still sniffing four scents twice a day for months, and a Mayo Clinic doctor describes half of patients as seeing no improvement after standard care. [24][18]
People whose loss is invisible to them — Two-thirds of previously infected people who reported no change in smell scored as having reduced smell on a 40-odour test, so they are missing from every count based on asking. [19]

What nobody knows yet

Open questions from across today’s stories — ours included.

01

How many smells a person can actually tell apart.

Estimates have run from about 10,000 to more than a trillion. The trillion figure comes from a 2014 paper in Science and is still described in the literature as provocative. [10][11]
02

Whether a smell really is a pattern across many receptors.

The textbook says yes. A 2025 study that matched human receptors to single molecules - cork taint, grapefruit, ambergris - states in its own summary that this challenges the combinatorial model. [1]
03

What losing your smell means for one particular person.

An ear, nose and throat doctor at Mayo Clinic is quoted saying older adults with unnoticed total loss have a nearly 100% chance of a severe neurodegenerative disorder within five years. A clinician quoted in New Scientist puts unexplained smell loss at about one in ten going on to Parkinson's. Both cannot be right for the same person. [18][28]
04

Why poor smell tracked heart disease and then stopped.

In 5,142 older US adults the risk ratio was 2.06 at two years and 1.08 by 9.6 years. No mechanism is named, and a signal that fades like that is hard to read. [31]
05

How much of olfactory training is the training.

Smell also returns on its own, and the meta-analysis found its largest effects where a drug or supplement was added to the sniffing rather than in the sniffing alone. [23]
06

Whether aromatherapy trials measure the oil or the expectation.

You cannot hide a smell from the person being tested. One review of 13 studies reports study-to-study disagreement of 88.7% on sleep quality, which is very high. [47]
07

How many working smell receptors any individual has.

The reference human genome carries 391, but about 60% of the wider family is broken by mutations in most populations, and which genes are broken differs from person to person. Nobody publishes a per-person count. [1][7]
08

Whether the bacteria in the nose affect smell or merely travel with it.

The review states the evidence is largely indirect and does not establish which way the arrow points. [41]

04 Hope carry this

The lining inside your nose is one of the few parts of the nervous system that keeps making new nerve cells for your whole life. After severe damage, glands beneath it that normally only produce mucus start generating replacement cells too.