The Sense of Smell

Smell is one of the chemical senses, the other being taste. They are so called because they sense chemicals, and smells are, of course, chemicals. With these senses we sample our environment for information. We are continuously testing the quality of the air we breathe (this will alert us to potential dangers, e.g. smoke) as well as using this sense to inform us of other relevant information, such as the presence of food or another individual. The chemicals detected by our sensory systems need to have certain properties. For instance, odour molecules must be small enough to be volatile (less than 300-400 relative molecular mass) so that they can vapourise, reach the nose and then dissolve in the mucus. This tells us that smell, unlike taste, can signal over long distances (an early warning device). We appear to have an innate ability to detect bad, aversive smells. One-day old babies give facial expressions that indicate rejection when given fish or rotten egg odour.

But, is our olfactory system doing more than just giving us warnings? Yes, of course. Amongst other possibilities, it serves a recognition function. We all have our own unique smell (some more pleasant than others! - but that's another story, see "mate choice" below) and can recognise and be recognised by our smell.

Dogs can distinguish between the smell of T-shirts worn by non-identical twins (they couldn't tell the difference between identical twins - presumably because they smell identical!). Children can distinguish between the smell of their siblings and other children of the same age. Babies recognise their own mothers' smell and mothers recognise their own babies' smell. Emotion can be communicated by smell. Dogs and horses are very sensitive to the smell of fear in humans. Recent research has shown that a panel of women can discriminate between armpit swabs taken from people watching "happy" and "sad" films. Men were less good at this. The emotions of others, for example fear, contentment, sexuality, may therefore be experienced and communicated by smell. Memory is often associated with smell. Smell and memory are intimately linked - although this phenomenon is not well understood (see Smell & Memory, below).

How we smell (some estimates suggest we can distinguish around 10,000 different smells - but see "Odour Code" below), why we smell and the impact of smell on our everyday life are poorly understood. We certainly underestimate the importance of smell to our well-being - ask an anosmic (someone who has lost some or all of their sense of smell). Some anosmics suffer from depression and their quality of life is severely affected - at the moment there is little that can be done to help them.

There are suggestions that smell can influence mood, memory, emotions, mate choice, the immune system and the endocrine system (hormones). We can communicate by smell - without knowing it. In fact the sense of smell could be said to be at the mind-body interface.

What a wonderful gift the sense of smell is! Think of the amazing smells of the various foods in the world- chips, fry ups, cooked chicken, puddings, fruits. Here is a list of different smells both pleasant and unpleasant taken from the website Medical Daily.

1. Fragrant

The research team lumped fragrant smells in with perfumery, floral, cologne, and rosy smells. Fragrant scents are the ones that seem light and natural, what is typically described by perfume and cologne manufacturers as “grassy” or “herbal.”

2. Woody/Resinous

Your nose easily picks up deep, earthy smells that remind you of the outdoors, the researchers claim. The smells are distinct to nature, which makes them easily recognizable. The team included with woody/resinous scents of musty, moldy, heavy, burnt, and smoky.

3. Non-Citrus Fruity

Opposite the hearty musk of the outdoors are the light, fresh scents associated with strawberries, banana, and certain perfumes that draw upon these natural aromas. Unlike the sharp, bitter freshness of lemon, non-citrus fruit smells may feel more “smooth” or “silky” to the nose.

4. Sharp/Pungent

You know it the moment you smell it. These smells include sour milk, fecal matter (e.g. manure), sweat, and the natural smell of things that have turned putrid or foul. These scents make you reel the instant you detect them. Oniony and garlicky smells also fall into this category.

5. Chemical

Your nose is particularly adroit at detecting synthetic smells. Even the most realistic perfume has its limits. It’s for this reason you’re able to quickly sniff out bleach and gasoline, or paint and felt tip markers. Researchers also included alcohol and disinfectants in the category.

6. Minty/Peppermint

Described as cool, fresh, exhilarating, the minty/peppermint smell has perhaps no rivals in the scent world. It’s become synonymous with cleanliness and is ubiquitous among oral hygiene products for this very reason. The researchers also include spicy in this category.

7. Sweet

Diverging from sweetness detected in fruit, the researchers classified as "sweet" the aromas of things like chocolate, vanilla, almond, and malty scents. They’re warm, and often light. Oftentimes they’ll be sold as “creamy” or “rich.”

8. Popcorn

Popcorn as the figurehead for the group may be jarring, as its neighboring groups are so unmistakable (not to say popcorn isn’t). But popcorn was grouped with other distinct smells, such as peanut butter, burnt, nutty, heavy, and warm. It’s that earthy smell that isn’t quite grass or wood.

9. Sickening

Sickening and decaying smells are a step beyond sharp/pungent smells. It’s sewage, burnt rubber, sulfuric acid, and household gas. Sickening smells are those that cause you to dry heave when the nose detects them in heavy enough concentrations. They aren’t merely “unpleasant;” they’re usually insufferable.

10. Lemon

Who could forget the trusty scent of lemon? Used in cleaning products for decades, the scent of lemon and citrus connotes freshness — like mint — with a hint of sweetness and sharpness that makes it unique from the others. It’s light and acidic, and the nose knows it instantly.

What things do we like the smell ? Personally I love loads of different smells,particualrly related to food. These include eggs cooked in a variety of ways, chips, sausages, mashed potatoes,a well done stake. I also love the smell of my Motorcycles especially when I've started up the engine-the smell of petrol ,oil, smoke! I lovd the smell of my children when they were babies, the smell of my wife when we are close together-the smell of her perfume. I loved the doggy smell of my wheaten terrier when he was alive. The smell of freshly cut grass, the smell of Roses, the smell freshly baked bread. I thank God today for the gift of smell. Thankyou God.