Their lids gleam under the shop lights: bottles made of elegant black or vivid green glass stand alongside white tubes with bold, minimalist lettering. These beauty products make many claims: to “defy” age, minimise pores, block pollution, plump skin. They promise radiance, illumination, hydration, brightening and perfecting. In many ways, they are no different from the beauty products that have come before them, except that they all claim to be somehow morally better, or cleaner. This is the new era of “clean beauty” – one that promises “no nasties”, and a “chemical-free”, “nontoxic” skincare regime. It is one that attempts to divide beauty products into good and bad, clean and dirty, toxic and nontoxic. But is there any scientific evidence for this? Do we really need to “clean up” the products we use on our faces? Are the products we may be using harmful – or is this just another way to sell us (often very expensive) creams that we don’t need?

There is certainly money to be made. Women in the UK are spending more than ever on facial skincare. According to the market research firm Mintel, 92% of us use a facial cleanser, 66% a day cream and 48% a night cream (up from 39% in 2017). Last year, the UK beauty industry was worth £1.15bn, and is expected to grow by 15% in the next five years.

The term “clean” in cosmetics is woolly. “Within ‘clean beauty’ there are many, many different elements,” says Sarah Meadows, the head buyer at the beauty chain Space NK. “Whether it is about sustainability, whether it is vegan, conscious living, free-from … playing into any of those would make you a clean brand. It can be fairly confusing for the customer.”

With shoppers keen to reduce their environmental impact, it makes sense to focus on sustainability – for example by using recyclable packaging. But the argument is less clear when it comes to the growing market in “free-from” products, which omit ingredients that the brands have deemed bad for some customers. The French cosmetics firm Officinea has even developed an app that can scan a product’s ingredients list to flag “controversial” chemicals.

“I train all of our new staff, and I have to really press on them that this is the view of that brand,” says Niamh Butler, the training manager at Space NK. Because even the makers of “clean” products can’t agree what substances we should be avoiding or embracing. Some, such as Tata Harper and Holland & Barrett, put an emphasis on the ingredients all being “natural”, while Drunk Elephant, a US brand that recently launched in the UK, warns consumers of the “suspicious six”, a handful of ingredients it claims are at the root of almost all skin complaints. It even sells kits with magnifying glasses so customers can identify these “harmful” chemicals in rival products they may already have at home.

There are, however, two ingredients that have been ditched by almost all “clean beauty” advocates: parabens and sodium lauryl sulphate (SLS). Parabens are preservatives that help products last longer, while SLS is a surfactant that helps to remove oils and allows foams to form, meaning it cleans, and produces the lather we see in shampoos and shower gels.

Sarah Willson, an assistant category manager for beauty at Holland & Barrett, says the company removed both ingredients from its clean beauty range because they “irritate” customers’ skin – although she admits that it hasn’t cut out all ingredients with the potential for irritation. It has focused on those two, she says, because SLS – and its chemical cousin sodium laureth sulphate (SLES) – and parabens “are used in everything … they are in your toothpaste, your mouthwash, your hair, your skin lotion. Because they are used so much, that is then what causes a mass irritation. It is not small-scale – a lot of people get an irritation.”

Dermatologists tend to disagree. Consultant Dr Anjali Mahto says that SLS can occasionally be problematic, but it depends on the person, and whether a product is left on or washed off. And if it is designed to be left on, it will have lower concentrations anyway. Prof Richard Guy, an expert in skin barrier function at the University of Bath, says that whether SLS triggers irritation depends on the individual, on the levels in a product, how much is used and where on the body it is applied.

“For example, someone with eczema, who has a weakened skin barrier, may be more vulnerable because more SLS can be absorbed, increasing the likelihood of irritation,” he says. “Equally, skin barrier function varies across different parts of the body – the eyelids, for instance, are less well protected.”

So should we shun it? According to Guy: “Given that SLS is still found in many personal care products, this suggests that it is generally being used at sufficiently low levels that irritation is avoided.” While SLS can be made from palm oil or coconut oil, its direct impact on the environment is relatively small as it quickly degrades.

What about parabens? Read clean beauty blogs and you’ll learn that they are “hormone disruptors”, and have been linked to cancer. Holland & Barrett’s clean beauty page says that “some research suggests that [parabens] may disrupt the way our bodies work (although parabens haven’t been directly linked to any serious health conditions)”.

Research in the area continues, but Cancer Research UK’s website says that while parabens have similarities to oestrogen – high levels of which can increase the risk of certain cancers – they are far weaker and “any effects are likely to be overwhelmed by natural oestrogen produced in our body, or similar chemicals found in our diet”.

“The UK and the EU tightly regulate how chemicals are used in products, and this includes parabens,” says Katie Patrick, a health information officer at Cancer Research UK. “For most chemicals, what’s important is the dose we’re exposed to. Most things have the potential to cause damage, but only at levels far higher than we’d ever experience in cosmetics or day-to-day life.”

Gary Moss, a senior lecturer in pharmaceutics at Keele University, agrees, saying that the skin is very well evolved to keep things out. “Parabens can permeate the skin,” he says, “but it is not just about whether things can get into and through the skin, and therefore into the body, but how much of it can penetrate the skin and at what rate.”

I ask Tiffany Masterson, the founder of Drunk Elephant, why she has cut out parabens, and she says: “I don’t think they are bad for you.” So why ditch them? “Consumers don’t want them.” And perhaps it really is that simple. If we are told that something is bad for us – whether that is backed by evidence or not – as consumers we will try to avoid it.

So what about the other ingredients Masterson tells her customers to avoid, such as essential oils, fragrances and “chemical screens”? “They are incompatible with the skin organ itself,” she says. As the Drunk Elephant website puts it, they are “the ingredients we feel are at the root of most skin behaviours we see, including oily, acne-prone, inflamed, sensitive, combination, dry/dehydrated and more”.

Masterson describes some of these six ingredients as “toxic” – although, as Moss points out, all things are toxic if taken in the wrong dose, and EU regulations mean cosmetics can only contain ingredients and concentrations deemed safe.

“I think [these skin problems] are more of a result than we are led to believe of what we put on our skin,” Masterson says. “Everyone has hormone fluctuations, there is absolutely this thing with teenage acne – that is true – but when your skin is healthy and it is not in a reactive mode because of what you are using every day, then it can weather those storms much better.” (She adds, though, that her daughter, who only uses “clean-compatible cosmetics”, sought help from a doctor for her teenage acne.)

Mahto, however, says “there is absolutely nothing wrong with most” of the ingredients Masterson singles out. If you suffer from eczema or sensitive skin, you should avoid essential oils, but most people have nothing to worry about. The problem with blaming people’s skin problems on the products they use is that it “completely fails to take into account people’s own hormones and genetics”, she continues. “All I think that does is create guilt among people who can’t afford to buy these products – that they are doing something wrong by not spending all this money on ‘clean’ healthcare, and that is why they have skin issues.”

Surely, the “cleanest” approach to cosmetics would be to not use any at all. “That’s like saying that, instead of eating junk food, we just eat nothing,” Masterson says. “I think you need to nourish your skin, I think some skin needs oil and hydration. Younger skin doesn’t need as much, but, importantly, as we mature, our skin cells don’t turn over as rapidly. We can use help with chemical exfoliation, antioxidants are great, physical protection is necessary, you need to cleanse your skin because there is dirt in the environment …”

Mahto takes a simpler approach. “We should all be washing our faces morning and evening,” to remove dirt, she says, adding that as the weather gets colder it can become necessary to moisturise, while sunscreen is important if spending time outdoors in the summer. But she adds it is not necessary “to layer 20 different products on in the morning”.

So how did we get here – to thinking that we need “cleaner” products to put on our faces? “I think people are inherently scared of chemicals and chemical names that they don’t understand, or they can’t read on the backs of their products, and that has led to this kind of drive of: if it is ‘clean’ and it is ‘natural’, it is somehow better for you. And that is absolutely not the case,” says Mahto, stressing that it is the concentration and dose of an ingredient that matter most. While “clean beauty” is not bad in itself, “it’s unnecessary”, she says. “It creates and propagates a myth that ‘chemicals’ are bad and ‘clean’ is better or more virtuous.” And this, in turn, leads to a move away from scientific fact. “Even ‘clean’ products have the ability to cause sensitivity and allergy,” she adds.

It seems that when it comes to cutting out ingredients, it’s really just about individual choice. David Colquhoun, a professor of pharmacology at University College London, has no patience for what he calls the cosmetic industry’s “made-up slogans”. “But if people have the money and wish to pay for it,” he says, “it is probably not going to harm them.”