Understanding your sense of smell

Smell is the first of the senses to develop and is more powerful than you think. Plus, learn how to make your own perfumed pick 'n' mix.

Whether it’s the tantalising aroma of a cake in the oven, the summery scent of salty ocean air – or even less appealing whiffs like traffic fumes – the world is full of fragrance. Your sense of smell is a potent tool that affects everything from appetite to mood, and it reaches the peak of its powers when you’re in your late teens.

THE SCIENCE BIT: HOW WE SMELL

So, how do you smell? The air contains miniscule scent molecules, which get caught in the mucus covering the back of your nose when you breathe in. The receptor cells on this sticky little patch fire up, sending messages to the olfactory bulb – a small area of the brain that lies roughly behind the eyes. Each odour sets off a different combination of the olfactory bulb’s 40 million receptor neurons, generating its own unique message.

UNFORGETTABLE FRAGRANCES

Unlike the messages generated by other senses, those from aromas are sent straight to areas of the brain that deal with emotions and memories. This might explain why certain smells can spark
strong feelings.

Studies show that, while memories of sights and sounds change over time, scent memories stay the same forever. Scientists aren’t sure why this is, but some think it’s to do with safety. Accurately remembering the smell of smoke or poisonous foods, for instance, could be a crucial way to avoid danger. Others believe scent memories are the most deep-rooted because smell is the first sense to develop – it begins in the womb.

NOTICE YOUR NOSE-POWER

As with all sorts of things that happen automatically in your body, it’s easy to take smelling for granted. But some people are born without this sense or develop an inability to smell (known as anosmia). There are also about 100 recognised forms of ‘specific anosmia’ – a condition that makes it impossible to pick up particular scents, such as garlic, chocolate, or cinnamon.

These long-term problems are rare, but most people know how hard it is to smell when you’ve got a blocked-up nose. If the patch at the back of the nose gets swollen, it can be tough to taste much of anything. This is because air is pushed up the nasal passage when you eat and the smell of food enhances its taste.

So next time you’re savouring the chef’s signature dish, running a bath with your favourite aromatherapy oils, or simply checking whether the milk is sour, bear in mind just how astounding your sense of smell is. This incredible identifier of odours helps you to make sense of the world and explore it safely. It’s certainly not to be sniffed at.

10 ODD OLFACTORY FACTS

1. Without a sense of smell, raw onion and apple taste very similar.
2. The average adult can distinguish between around 10,000 different smells.
3. Dogs have nearly 44 times more scent cells than humans, which is why sniffer dogs woof at any incriminating whiffs.
4. Olfactory receptor neurons are the only nerve cells in the body to be replaced regularly – every four to eight weeks.
5. Phantosmia is the sensation of smelling odours that aren’t really there.
6. Baking bread frequently tops polls of ‘favourite smells’.
7. The word perfume comes from the Latin per fuma (‘from smoke’). Fragrances used to be released through incense.
8. Emotions such as fear and happiness can be detected in the smell of sweat.
9. Legend has it that Egypt’s queen Cleopatra soaked the sails of her ship in perfumed oils so Roman general Mark Antony would smell her beautiful scent on the breeze before she landed.
10. In humans, the sense of smell completely shuts down during sleep.

HOW TO MAKE A PERFUMED PICK ‘N’ MIX

Homemade potpourri gives your nose a treat and can be a lovely way to bring the floral aromas of the outdoors inside. Follow these easy steps and breathe in your very own blend.

1. Gather flower petals, leaves, and seedpods from around your backyard or garden to create the body of your potpourri, choosing decorative shapes and pretty colours. Sturdy, aromatic leaves such as sage and rosemary work well, and rose petals are a traditional choice. Always ask permission from whoever does the gardening before collecting any parts of a plant.
2. Spread the items you’ve gathered on a tray or plate and leave to dry.
3. In a wooden or ceramic bowl, mix a few drops of your favourite floral essential oil with a fixative such as orris root powder. (Find this in health food shops.) Leave to infuse for a few days.
4. Add the dry ingredients to the bowl. (Make sure it’s not a metal bowl, as this can taint the potpourri.) Mix, and cover with a cloth.
5. Put aside and allow the scent to develop for around a month, checking regularly. When the smell is strong enough for you, the potpourri is ready to be used.
6. Pour it into a bowl and put it on display, or divide into small drawstring muslin bags to pop in a clothes drawer or under your pillow.