Have you ever wondered why people smell different even though they wear the same perfume? Individual skin naturally contains a particular cocktail of chemicals that, rather like a fingerprint, leaves a unique aroma. When perfume blends with a person’s body odour it takes on a life of its own and creates a unique mark of identity.
At perfumeries, fragrances always smell just as their creator designed them. But they take on a different life on individual skin. We now know that we all give off a different body odour because everyone’s skin is composed of various chemical substances that, on evaporation, are transmitted by air and can be perceived by smell. These substances, known as volatile organic compounds, are part of all living organisms. Humans secrete them though two types of skin gland that produce sweat: eccrine and apocrine glands. When we apply a perfume, our natural body odour and the fragrance blend together and produce a specific, unique cocktail. But how do they blend? And why, once we are wearing it, does a perfume smell nothing like its creator planned?
The underarm areas (axillae) are the parts of the body that perspire the most and so contribute most to body odour. Whether pleasant or unpleasant, body odour is the result of a mixture of volatile chemical substances from underarm perspiration — steroid hormones, fatty acids and sulfur-containing compounds — that react when they come into contact with the microbial flora of the skin.
The flora contains bacteria from a wide variety of species, such as staphylococcus or coryneform bacteria, whose main function is to protect and nourish the layers of the skin. In coexisting in varying amounts and combinations in our skin, these microbes leave a different trace in each person. They transform non-odorous natural secretions into volatile molecules that smell.
What happens if perfume is added to this cocktail?
When fragrances are mixed with the cocktail of skin molecules, they trigger a series of chemical reactions that produce a unique smell. The quality and intensity of the smell depends on the amount of fragrance the skin absorbs and how much evaporates. By placing clothes on perfumed skin, we ensure product absorption and less evaporation.
The degree of moisture emitted by the pores of the skin can also influence the amount of fragrance that evaporates. Perfume applied to well-hydrated skin that produces a lot of moisture in a dry room at a high temperature will evaporate more quickly. Covered skin is also hotter and probably the stratum corneum stays well hydrated.
All these factors determine our body odour when we use perfume. But let’s take a look at what other substances in our skin modify our body odour when they blend with our perfume.
Fatty acids and microflora
Perfume molecules, which dissolve when mixed with fatty acids, also interact with other epidermal fats (ceramides and cholesterol). These substances, present in individual skin in varying amounts and proportions, are the first barrier to perfume being absorbed through the skin.
And, as we have already said, skin microflora — with species that vary from person to person depending on several factors such as age, lifestyle, diet and stress — react with the molecules of fragrances and create different smells.
Science has already identified nearly 100 volatile organic compounds produced by human skin. Various combinations between the characteristics of our skin, the environment and perfume molecules create an endless number of smells, each virtually unique.
Smell: a distinguishing feature
We recognise and remember the smell of people close to us because our sense of smell has developed to detect odours that have an emotional or sexual meaning. That’s why choosing a good perfume is vitally important for many people who use the lingering trace of perfume as their mark of identity.
How to choose a perfume
On the day of purchase don’t wear any kind of perfume, cologne or lipstick.
Only use the paper test strips to rule out the fragrances you don’t like. Choose just two perfumes.
Place a small amount of perfume on the inside of your wrist. Wait two or three minutes for the alcohol to evaporate and for the perfume to interact with your skin.
Do the same with the other fragrance on the other wrist.
Wait a few seconds before smelling each one so as to avoid mixing aromas.
A word of advice: it’s best not to buy a perfume the same day as you test it. It’s a good idea to let it act, check its effect after a few hours and then go back to the store when your mind is made up. Better still, take home a few samples and test them at your leisure.
Once on the skin, all perfumes are released in three aromatic phases. During the first (lasting around 15 minutes), we perceive citrus notes. In the second phase (after around two hours), we notice the core of the fragrance (woods, floral aromas). And finally, we identify spices, sweet aromas and musk. If you like a perfume during all three phases, then that’s the one for you.
Not all perfumes are suitable for all kinds of skin. Choosing the right one for you can be a difficult task — some even say it’s an art…
By Núria Estapé, science journalist
Sources: British Journal of Dermatology