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doodlesense

WHAT THE SCIENCE SAYS

Most of flavour
is really smell.

1,000 receptor genes

  • Smell shapes flavour
  • Changes are common
  • See a GP if it lasts
  • The quiet sense, explained

Your nose does more of the tasting than your tongue.

Smell cells high inside the nose pick up molecules from the air and from food as you chew. Together they let us tell apart thousands of odours, and warn us about smoke, gas and food that has gone off.

Updated

Check a change

THE SHORT ANSWER

A thousand sensors,
one pattern.

Each smell cell knows only a few odours.
The brain reads the combination.

RECEPTORS

A huge gene family

Work recognised by the 2004 Nobel Prize found some 1,000 genes for smell receptors, and showed each smell cell carries just one type.

See the numbers

FLAVOUR

Smelling as you chew

Aromas from food reach smell cells through a channel from the back of the throat. Block it with a cold and food tastes bland.

How it works

CHANGES

Often temporary

The NHS says a changed sense of smell is not usually serious and may get better in weeks or months. Smell training helps some people.

Check a change

General information only, not medical advice. For advice about your own health, speak to a doctor, pharmacist or other qualified health professional.

A QUICK CHANGE CHECK

What kind of
change is it?

Pick a change to see its name and what the NHS and the US National Institute on Deafness and Other Communication Disorders say about it. The bar shows how much of the sense is affected.

Change check

Choose a change
A little weaker with ageCommon

The NHS says it is common to lose some of your sense of smell as you get older. NIDCD adds that problems are more common in men.

Smells seem faintHyposmia

A reduced ability to detect odours. Colds, flu, sinus infections and allergies such as hay fever are among the most common causes.

Familiar things smell wrongParosmia

A change in how things smell, for example something that used to smell pleasant now smells foul.

Smelling things that are not therePhantosmia

Sensing an odour that is not there. The NHS gives smoke or burnt toast as examples.

No sense of smell at allAnosmia

The complete inability to detect odours. The NHS warns you may not be able to smell gas leaks, fires or food that has gone off.

Sources: NHS, Lost or changed sense of smell (reviewed December 2023); NIDCD, Smell disorders.

General information from NHS and NIDCD pages, not a diagnosis. See a GP if your sense of smell does not return to normal in a few weeks.

TWO NUMBERS WORTH KNOWING

A big share
of our genes.

How much of our DNA goes on smell,
and how often it fades in later life.

≈ 1,000

Genes for smell receptors

The 2004 Nobel Prize announcement describes a gene family of some 1,000 genes, about three per cent of our genes, behind an equivalent number of smell receptor types.

RECEPTOR GENES · NOBEL ASSEMBLY

≈ 1in 4

Men aged 60 to 69 with a smell disorder, one study

NIDCD says nearly a quarter of men aged 60 to 69 had a smell disorder in one study, against about 11% of women of that age.

LATER LIFE · NIDCD

NIDCD says one to two percent of North Americans report problems with their sense of smell, and that problems increase with age.

FOUR THINGS TO KNOW

If your smell
goes or changes.

Four small unlabelled amber glass jars on a table, with a lemon, a rose, cloves and eucalyptus leaves beside them
AI-generated image, not a photograph of a real person or place.

These come from NHS guidance and the smell loss charity AbScent, which the NHS points to. They are general information, not a treatment plan.

  1. Give it a few weeks

    The NHS says smell may return to normal in a few weeks or months, often after a cold or infection clears.

  2. See a GP if it lasts

    See a GP if your sense of smell does not go back to normal in a few weeks. They can check for causes such as sinusitis or nasal polyps.

  3. Ask about smell training

    AbScent describes sniffing the same four scents every day, around 20 seconds each, usually for at least four months.

  4. Know what you might miss

    The NHS warns that without smell you may not notice gas leaks, fires or food that has gone off.

SMELL AND FLAVOUR

Two routes
into the nose.

Hands rubbing fresh rosemary and basil leaves over a chopping board, releasing their scent
AI-generated image, not a photograph of a real person or place.

NIDCD explains that smells reach the smell cells through the nostrils and through a channel linking the roof of the throat to the nose. Chewing releases aromas that travel this second route, which is why a blocked nose makes food taste of little.

Some people who think they have lost their sense of taste find they have lost their sense of smell instead. The 2004 Nobel announcement notes that when something tastes really good, it is mainly the smell system that detects the qualities we enjoy.

Questions

Questions people ask

How many smells can people recognise?

The 2004 Nobel Prize announcement refers to recognising and remembering about 10,000 different odours, using around 1,000 types of smell receptor in combination.

Why does food taste bland when I have a cold?

A blocked nose stops aromas from chewed food reaching the smell cells through the channel at the back of the throat. NIDCD says without smell, foods tend to taste bland.

Is losing my sense of smell serious?

The NHS says it is not usually serious and may improve in weeks or months, but advises seeing a GP if it does not return to normal in a few weeks.

What is smell training?

A routine of sniffing the same set of scents daily while concentrating on them. The NHS says it can help some people and points to the charities AbScent and Fifth Sense.

Do dogs really smell better than us?

The Nobel announcement says the smell-sensing area in a dog's nose is some forty times larger than in humans.

Sources

Where the facts come from

  1. NHS: Lost or changed sense of smell
  2. NIDCD (US National Institutes of Health): Smell disorders
  3. NobelPrize.org: Press release, Nobel Prize in Physiology or Medicine 2004
  4. AbScent: Smell training

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