By Emily Mee, news reporter
Delve into the world of the perfume industry and you'll quickly realise how little you know about how our favourite fragrances are made and what's in them.
This is no accident. If you pick up a bottle of perfume, you'll find its ingredients list often uses catch-all words like "parfums" or "fragrance".
That's because what's in each perfume - known as its "composition" - is closely guarded as a trade secret.
So closely guarded, in fact, that even perfumers in the same company are said to not know what's inside the fragrances their colleagues are working on.
Mysterious perfume houses you've likely never heard of supply most of the well-known brands, with the same perfumers often producing fragrances for the likes of Chloe and Yves Saint Laurent as well as the budget companies.
All this secrecy has helped some fragrances to become iconic and unique. Think Chanel No5, or Yves Saint Laurent's Opium.
But in recent years, these high-end brands have been waging a silent war - against the rise of the perfume "dupe houses" trying to copy their fragrances.
'Just like the designer brands'
Designer copycats have existed for some time - but if you've started hearing the word "dupe" everywhere lately, it's because TikTok creators are increasingly promoting these cheaper alternatives.
Dupes are products that appear very similar to a more expensive or high-quality product.
Increasingly, companies have been popping up offering fragrances "inspired by" designer brands.
They're known as dupe houses, and while they're not pretending to be the real thing, they're not trying to hide what they're copying either.
Two of the most well-known are Noted Aromas, which reportedly hit £4m in its first year of business, and The Essence Vault.
Others also include Dossier, A.L.T Fragrances, Eden Perfumes, Oakcha and Montagne.
Noted Aromas claims on its website that its fragrances smell "just like the designer brands" and it says they are "near exact copies without the high prices".
Some of its scents include Lisbon, which is listed as "Inspired By Sauvage", and Monte Carlo, "Inspired By Baccarat Rouge".
Separately from all this, high street brands like Zara, M&S and H&M produce low-cost perfumes that are frequently touted by consumers as dupes for high-end fragrances.
Because they don't use similar branding or packaging, it's unclear how much is intentional and how much is the result of following the same trends or innocuously using similar ingredients.
However, an industry insider told Sky News it's "not by accident that they smell the same" and there are plenty of examples of this happening in the industry.
They said brands will often approach perfumers with a brief asking them to create something "heavily inspired" by a fragrance that is already successful as they know it sells.
Zara, M&S and H&M all declined to comment for this piece or did not respond to our requests.
Only 1% of a perfume's price is the actual fragrance
It's not difficult to see why consumers are turning to dupes.
Plenty of high-end perfumes are in the three-figure range - with some even reaching as high as £300.
Many people are now "priced out" of top brands, particularly in the cost of living crisis, said Amir Awan, the co-founder and chief executive of Dupeshop.
His website, which tests affordable alternatives to high-end products, has more than a million users. It does not promote products from the perfume dupe houses, instead suggesting products that are similar based on its own testing.
"People are having to budget more than they ever have and they’re having to cut back on spending on beauty," Mr Awan said, adding that customers are now "more open to dupes than ever".
Questions are also being raised about whether customers are actually getting their money's worth.
In many cases, only 1% of the price the customer pays is actually for the liquid - or "juice" - itself.
Much of the money that high-end brands spend is on marketing, celebrity-led advertising campaigns and expensive bottles, and it's well-known that perfumes have high product margins (hence why you'll see many brands selling fragrances).
That's according to Dariush Alavi, who writes perfume blog Persolaise and also authored the book Le Snob: Perfume.
In some cases, customers are paying partially for the brand's heritage and status.
This helps to explain why dupe brands can offer very similar fragrances for a fraction of the price.
Master perfumer and industry whistleblower Christophe Laudamiel wrote in an open letter called Dear World that fashion brands "get perfumes as cheap as possible from a fragrance house to put it in a bling bling bottle and sell it as expensively as possible".
Meanwhile, perfume critic and biophysicist Luca Turin said the cost of perfume formulas has been "going downhill for years", except when it comes to natural ingredients, so there is little justification for many brands' sky-high prices.
However, he said dupe houses arguing they make perfumes more accessible was "self-serving tosh" and that "plagiarism sucks".
What goes in to making a perfume?
Dupes are a highly contentious issue within the perfume industry.
Mr Alavi describes them as "completely unethical, completely immoral".
He says he's not defending the high prices of the perfume industry, but when you buy an original perfume, you are often paying for the perfumer's "years and years of experience", creative thinking and ideas.
"I don't know how you put a sum of money on that," he said. "The cost of a Picasso isn't dependent on the cost of the paint that is actually physically present on the canvas. We don't add up how many reds and blues and greens he's used and go, okay, this is how much we expect it would cost therefore this is what the painting should cost."
Beckielou Brown, perfumer and co-founder of all-naturals fragrance brand Altra, explained that the creative process to make a singular fragrance can take between six to 12 months.
Perfumers need to know "hundreds of different ingredients and what they do", and having the skills to create a quality fragrance takes years of practice and experimentation.
Like Mr Alavi, she described creating a fragrance as a form of artistic expression.
The process can involve many forms of inspiration, such as a place, era, person, or feeling, and is a "labour of love".
She pointed out that in most other creative industries, creators are protected by copyright law - but it's near impossible to trademark a fragrance.
Trademark law is generally not designed to protect items with a practical use - so perfume smells can't usually be trademarked because their function is to make you smell good.
That means dupe houses can take advantage, so long as they are not selling counterfeit products.
Ms Brown said dupe houses are simply "profiting from other people's investment without having to do any of the work themselves".
"Independent perfumers go through a process that is personal, artistic and in depth. If that's just copied through reverse engineering a scent, it's sidestepping a whole process," she said.
How the dupe houses recreate fragrances
Okay, so how do you reverse engineer a scent?
Some of this can be explained by the fact perfumers are highly trained. They will be able to copy things by smelling them, and can use their expertise to try recreating a scent before tweaking it.
It's also thanks to technology called gas chromatography.
This can be used to detect banned substances in urine samples from athletes, or by forensic investigators to detect fuels that may have been used to deliberately start fires - but it can also identify the aroma compounds in a perfume sample.
Essentially, dupe houses can use the technology to work out roughly which ingredients have been used in a fragrance.
Perfumers are well aware of this. In fact, they're going to even greater lengths now to hide their compositions.
Mr Alavi says the brands that can afford to do it will deliberately instruct the perfumers to come up with a very expensive formula with pricy materials that are hard to emulate and difficult to find substitutes for - essentially pricing out the dupe companies.
Another technique is to "trick" the gas chromatograph by putting trace amounts of certain substances into the formula that can't be smelled in the finished product.
If there's enough of this material, it can skew the results from the gas chromatograph and make it difficult for the dupe houses to interpret.
Still, Mr Alavi said, dupe houses are managing to get around this: "If the industry had come up with some foolproof way of preventing the proliferation of dupes they would have done it by now. But it's not that easy."
'They're all copying each other'
There is an odd juxtaposition here.
On the one hand, perfumers are going to great lengths to prevent their original creations from being copied by dupe houses and the fragrance formulas are kept tightly under wraps as trade secrets.
In reality, according to Mr Turin, even the top brands are all copying each other and "chasing each other's tails".
Meanwhile, plenty of the companies selling perfumes to you don't actually create or even own the fragrances used in their products.
"Let's take a company like Dolce and Gabbana. If you are at Dolce and Gabbana, you don't make your perfumes yourself," says The Persolaise's Mr Alavi.
Dolce and Gabbana also does not own the formula.
In fact, most of the fragrances you buy are outsourced to a small group of perfume compounding houses - Givaudan, Firmenich and International Flavors & Fragrances (IFF).
Unless you're an industry insider, it's unlikely you've heard of them, and there's little information on their websites - but among them they have the best perfumers in the world.
The same perfumers will work with both luxury brands and more affordable companies.
Avon's global head of fragrance brands Victor Costa told Sky News that his company works with top perfumer Olivier Cresp from Firmenich - who has also worked with the likes of Chloe, Yves Saint Laurent, Thierry Mugler and Paco Rabanne.
The big-name brands will contact multiple perfume houses - often through a third-party - with a marketing brief on a new fragrance they would like made.
According to the blog Sommelier Du Parfum, it might be a brief like: "We are looking for a perfume for a woman between 25 and 35 years old, modern, urban, etc."
But it's at this point that a company might also ask for a fragrance similar to another brand's.
Mr Turin says all of the major perfume houses have a gas chromatograph allowing them to work out what their competitors are doing.
The perfume houses will then be put into competition and get teams of perfumers to formulate fragrances based on the brief.
The brand then chooses which fragrance it prefers and begins production.
Is there any hope of change?
Beckielou Brown said there should be "some kind of code of ethics" to change the industry - and she's not alone in thinking this.
The Perfumery Code of Ethics is an initiative created by Christophe Laudamiel, and it calls for perfumes to be protected by copyright law.
It also says there is "no place for plagiarism" and that perfumers should be fairly rewarded and credited for their work by the brands that are making huge profits out of them.
But with so little public awareness of how the perfume industry works, it's difficult to see much being done - and so the silent war goes on.