Written by Molly Steadman and Natasha Barrow, edited by Charlotte Pugsley and Caroline Babisz.
Retinol, Niacinamide, Salicylic acid. These “bioactive” ingredients have taken the skincare world by storm, trending all over YouTube, Instagram and TikTok. They claim to alter the way in which your skin functions on a molecular level to improve its appearance…which all sounds incredibly scientific and convincing. If you use Google to research these ingredients, it appears that every website, from Healthline to Vogue[1-6], is in agreement to their purported benefit. However, the evidence within scientific literature for bioactive ingredients is somewhat lacking. So, where is the ‘clinically proven’ evidence?!
Skin care products that contain bioactive ingredients have been dubbed ‘cosmeceuticals’ because they supposedly straddle the boundary between what is considered a cosmetic and what is a pharmaceutical. However, in the eyes of the UK Health Authority (the Medicines and Healthcare products Regulatory Agency, MHRA), there is no such thing as a ‘cosmeceutical’ - only cosmetics and pharmaceuticals. Products must be placed into either one of these categories and this has huge consequences on how much evidence is needed to verify a particular products’ performance. While medicines are required to undergo clinical trials to scientifically prove their effects, cosmetics require a significantly lower level of clinical data to satisfy regulations. So can we as consumers really trust the alleged benefits of bioactive skincare ingredients?!
First things first, let’s start with some definitions:
According to the MHRA, cosmetics are applied externally to the human body to clean, change appearance, protect or maintain. Whereas pharmaceuticals work to treat and/or prevent human diseases, and to restore, correct, or modify physiological functions by exerting a pharmacological, immunological, or metabolic action.
As there is no regulatory category for cosmeceuticals, all of the skincare products that you can buy over-the-counter are in fact cosmetics. If a product is “borderline”, falling between the definition of a cosmetic and a pharmaceutical, it will be classified as a pharmaceutical. Cosmetic companies want to avoid their products being regulated as pharmaceuticals as they will require far more time-consuming and expensive clinical trials. One way in which this is prevented is by being careful about what they state in their advertising.
Comparing both definitions, it becomes apparent that cosmetics can only really function to maintain the normal state of the human body. While medicines can actually treat the human body, to remove or prevent disease. This means cosmetics cannot claim to treat or prevent disease, like certain medical conditions like acne and eczema. Although they are allowed to say that they are ‘suitable for’ people with these conditions. They can also bypass the medical classification by claiming to reduce something that causes the disease, such as blocked pores or excess oil. However, this is only acceptable as the effect is accomplished through a cleaning action - falling well within the regulated function of a cosmetic. They can’t claim that they actively improve any skin concern and can only claim that they improve the appearance of it. This is because modifying physiological functions by exerting a pharmacological, immunological, or metabolic action are considered pharmaceutical functions.
So, although it is strategic to have these products marketed as cosmetics, could there still be a real and measurable physiological effect? If a product works well, consumers will be more likely to continue using them. There must be some evidence to suggest that these active ingredients actually DO something? Although the products state that they are ‘clinically proven’, meaning that they perform human studies in a clinical setting, this isn’t a very useful measure of the bioactive ingredients effect, as we now know that their performance claims can only be cosmetic - such as cleaning and improving appearance. Therefore, none of the data companies gather will look for objective measures of its molecular performance. For example, the outcome of clinical studies are often based on subjective consumer perception studies. This is where advertising campaigns will often make statements such as, “96% of participants said their skin felt smoother”.
Retinoids: When looking at the scientific literature, it’s hard to find a lot of information for many of the ’cosmeceutical’ ingredients. However, one of the most well-known and well-studied ingredients are the retinoids which are used for wrinkles, acne & psoriasis. They are derivatives of vitamin A which, when converted into retinoic acid within the skin, are able to bind to a type of cell receptor to promote cell proliferation, differentiation & apoptosis, thereby improving skin renewal[8].
Retinoic acid has undergone medical clinical testing and is licensed as an acne treatment. However, some of its derivative precursors, most commonly retinol, are present within cosmetics and are converted into retinoic acid within the skin.
So, how can an ingredient be used both in medicines and cosmetics? Well, for cosmetics the legal concentration of retinol within cosmetic products is usually capped at 0.3%. The amount of retinol that will be converted into retinoic acid will also be far lower than the total applied. Therefore, the concentration of active retinoic acid that could be achieved from cosmetics is far lower than that seen in pharmaceuticals. There are strict rules placed around the use of retinols in both medicines and cosmetics, because of the side-effects that have been identified with higher concentrations, such as skin peeling and liver damage.
Niacinamide: For other bioactive ingredients, the data is even more sparse. For example, niacinamide is an ingredient claimed to minimize pores & reduce sebum (oil) production[1,4]. However, there is only 1 peer-reviewed double-blind clinical trial published in 2006 testing its use within over-the-counter skin care products for sebum control. Participants either applied a 2% niacinamide serum or a placebo for 2-4 weeks. Although sebum/oil levels were measured in an objective way, some of their results did not show a statistically significant difference between the treatment and placebo groups. Although some comparisons were statistically significant, niacinamide treated participants had a minimal improvement of only ~10% less sebum production than the placebo controlled group.
To summarise; the clinical data for cosmetics is limited – so take any claimed “benefit” with a pinch of salt. It’s not necessarily that the benefits of bioactives are completely made up, as some are used medically at higher concentrations - it’s just that there aren’t published studies proving the physiological effect generated using the low concentrations present within cosmetics. In Japan they have an additional regulatory bracket for “quasi-drugs” for products with limited concentrations of active ingredients that produce mild effects. Perhaps if the UK were to adopt a similar regulatory system, it would encourage more research into bioactive ingredients. In fact, a recent UK government report indicates a potential new regulatory category for Nutraceuticals which would transcend the boundaries of the regulatory categories for fortified foods, food supplements and medicines. So, perhaps a regulatory category for cosmeceuticals may be foreseeable in the future. For now, as the consumer, we will probably still continue to use cosmeceutical products but perhaps we’ll think twice before spending more than we ought to on them.
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