The secret of scent: Why perfume fragrance is more about skin microbes than chemistry

Perfume performance has traditionally been explained through skin chemistry — pH, sebum, moisture, and temperature. But these traits are heavily influenced by our skin microbiome: the community of bacteria, fungi, and other microbes living on the skin. These microbes shape pH, lipid content, and hydration, and produce enzymes and acids — all of which can affect perfume fragrance

For as long as perfumes have existed, people have shared one common frustration: “This fragrance doesn’t work on me.” Some perfumes vanish within minutes. Others smell strangely different on your wrist compared to your neck. For some, a fragrance that turns heads when worn by a friend feels completely flat on their own skin. This phenomenon — universally felt yet poorly explained — has puzzled both consumers and perfumers alike.

It was this mystery that led me, an infectious diseases physician and a lifelong perfume connoisseur, to explore a radical idea: What if the answer lies not in the perfume bottle, but in the microscopic world living on our skin? What if bacteria — the very organisms I spent years fighting in hospitals — also held the key to unlocking better, more personal fragrance experiences?

Skin chemistry: Where explanation falls short

For decades, the performance of perfumes on skin has been explained through the lens of “skin chemistry” — a term referring to measurable physical and chemical characteristics such as pH, moisture, oil content (sebum), temperature, and hydration. These parameters are believed to determine how perfume molecules behave once sprayed on the skin: how fast they evaporate, how long they linger, and how true they smell.

For example, it’s commonly said that acidic skin, with a pH typically ranging from 4.5 to 5.5, may destabilise certain top notes like citrus or green florals. Oily skin is thought to hold on to heavier, oil-soluble base notes such as musk, amber, and oud more effectively, resulting in better longevity. Moisturised skin is often recommended as a base to help fragrance last longer, since dryness is believed to speed up evaporation. Similarly, pulse points — areas like the neck, wrists, and inside the elbows — are considered ideal for application because their warmth enhances scent projection.

These guidelines make intuitive sense, and they are widely shared by perfumers. But in practice, they don’t always hold up.

Even within the same individual, perfume performance can vary significantly across different parts of the body. A scent that smells radiant on the wrist may turn sour on the neck or vanish quickly behind the ears. All these are warm areas, but they differ in moisture, oiliness, and bacterial composition. The neck is more humid and richer in sebaceous activity, while the wrist is relatively dry with fewer oil glands. Still, these variables don’t consistently predict how a perfume will behave.

The limitations of this model become clearer when users describe common frustrations. A fresh floral fragrance might bloom beautifully on one person, yet turn sour, sweaty, or metallic on another — even if they have similar skin types. Citrus perfumes may sparkle on one site but develop a sharp, acidic edge on another. These aren’t mere issues of longevity; they’re transformations in scent quality, which static physicochemical factors alone struggle to explain.

This gap in understanding led me to investigate a more dynamic, biologically-driven model — one that considers not just the skin’s chemistry, but its living ecosystem.

The missing link: Skin microbiome

Perfume performance has traditionally been explained through “skin chemistry” — pH, sebum, moisture, and temperature. But these traits are heavily influenced by our skin microbiome: the community of bacteria, fungi, and other microbes living on the skin. These microbes shape pH, lipid content, and hydration, and produce enzymes and acids — all of which can affect how fragrance molecules behave.

Importantly, no direct in vivo studies have yet mapped how skin bacteria interact with perfume compounds on human skin. Such research is technically complex, costly, and commercially unexplored, as the fragrance industry has long prioritised universality over personalisation. Moreover, microbiome science is still maturing, and cross-disciplinary studies with fragrance chemistry are only beginning to emerge.

Yet indirect evidence is abundant. Environmental bacteria routinely metabolise volatile organic compounds like linalool, limonene, and eugenol — ingredients also found in perfumes — using enzymes like alcohol dehydrogenases and monooxygenases. Many of these enzymes (or their functional equivalents) exist in human skin bacteria. In the fragrance industry, similar microbial enzymes are even used to synthesise or alter scent compounds.

Meanwhile, body odour studies have shown how skin microbes like Corynebacterium and Cutibacterium metabolise sweat into distinctive volatile organic compounds, with microbial composition differing by body site (armpit, wrist, neck) — mirroring differences in perfume behaviour.

This growing body of indirect evidence suggests that microbial metabolism may significantly impact fragrance longevity and scent evolution. Why does a perfume smell fresh on one person but sour on another? Why does it last longer on the neck than the wrist? A microbiome-informed lens helps explain these variations.

By adding biology to the chemistry, we get a more complete picture. While pH and oiliness still matter, microbial presence and enzyme activity could be the missing factor that finally makes sense of fragrance performance variability.

How microbiome insights help personalisation

Perfume users often face frustration when scents don’t last or change unpleasantly on their skin. These mismatches lead to overapplication, discarded bottles, and repeated brand-switching — much of it due to unrecognised differences in skin microbiome.

Using the right perfume for one’s skin reduces the need for excess sprays, lowering exposure to chemicals that have been linked to irritation, allergies, and potential long-term health effects such as endocrine disruption, cardiovascular and respiratory side effects and even oncogenic potential. It also reduces waste. Natural oils require enormous resources — thousands of kilograms of rose petals or jasmine buds — while synthetic perfumes depend on petrochemicals. Yet many perfumes go unused due to poor fit.

Personalisation guided by microbiome insights — even without skin microbiome metagenomic testing — helps avoid overuse, minimises health risks, and respects the environmental cost of fragrance creation.

Metagenomic testing is optional, not essential

Metagenomic testing — analysing the genetic material of the microbes on your skin — can provide detailed insights into your skin’s bacterial composition. It can tell us which bacterial groups dominate a particular site, such as the wrist or neck, and help predict how they might interact with certain fragrance components. But while promising, this approach has its limitations.

The test is expensive, time-consuming, and not immediately scalable. It requires laboratory processing and takes several days to generate results. Most users looking for a new perfume aren’t willing to wait — or spend — that much for each decision.

More importantly, personalisation doesn’t have to depend on testing. The wealth of data already available from skin microbiome studies, body odour research, and environmental microbiology offers enough insights to guide intelligent perfume choices. By comparing known microbiome patterns across body sites and linking them to typical fragrance behaviours, we can offer meaningful advice — without swabs or sequencing.

In other words, testing may refine the experience for fragrance connoisseurs, but microbiome-informed personalisation is already possible for everyone, today.

A new perspective on personal fragrance

It’s time to update our thinking. For too long, perfume performance has been explained only in terms of skin “chemistry” — pH, moisture, and oiliness. But these factors themselves are shaped by the skin microbiome, a living, evolving layer of biology that varies from person to person and even across body sites.

We need to shift the conversation from skin chemistry variability to skin microbiome variability.

Understanding the basics of perfumery — how top, mid, and base notes behave, and how skin can influence scent — is essential. But understanding our skin’s invisible ecosystem is just as important. When perfume users are educated about the role of microbes in fragrance transformation and performance, they can make more informed, satisfying, and sustainable choices.

Any attempt to personalise perfume without microbiome insights — even when testing isn’t involved — remains incomplete. The future of fragrance is not just about scent; it’s about science. And that science starts with the skin microbiome.