Probiotic skincare: what microbiome products can do and what is just marketing

ACTIVE INGREDIENTS

What is the skin microbiome, and what does skincare have to do with it?

The skin microbiome is the community of bacteria, fungi and viruses that lives on your skin, and skincare mainly changes the conditions this community lives in. A review in Nature Reviews Microbiology describes the skin as a dry, nutrient-poor and acidic habitat. It is precisely these conditions that make it hard for pathogens to settle, and yet the skin is home to a diverse microbiota. The review focuses on species such as Staphylococcus epidermidis, Cutibacterium acnes (still under its old name, Propionibacterium acnes) and Staphylococcus aureus. One point is worth keeping in mind: there is no target value for which mix is ‘right’ for you. That is why no label can restore it.

A small study in BMC Biology shows what skincare actually does. Researchers followed 11 volunteers over 9 weeks to see how four everyday products changed their skin. The effects lasted for weeks and varied greatly from person to person. Face and arm lotions barely changed bacterial diversity, but they did change the chemical make-up of the skin’s surface. So a cream does not deliver bacteria; it is part of the environment the bacteria live in: moisture, lipids, acidity and the number of irritants.

Does probiotic skincare really contain live bacteria?

No, probiotic skincare almost never contains live bacteria, and that comes down to the rules for cosmetics. Probiotics are defined as live microorganisms that provide a health benefit when given in adequate amounts. A review in the journal Molecules points out that, for safety reasons, cosmetics should contain only very low numbers of microbes, and concludes that a true probiotic cosmetic cannot exist. There are also two practical hurdles: preservatives are there to inhibit or kill microbes in the product, and in a water-based cream, dried bacteria would either multiply or die.

The same review analysed 50 products marketed as probiotic from two large North American cosmetics retailers. Of the bacterial ingredients listed on the labels, 78 per cent were ferments in the form of extracts, filtrates or lysates. Yoghurt accounted for 10 per cent, with no indication of which bacteria it contained or whether they were alive. So ‘probiotic’ on a cream usually means that it contains something once derived from bacteria. That need not be worthless, but it is not what the term promises.

What is the difference between prebiotics, probiotics and postbiotics in creams?

Prebiotics are meant to feed certain skin bacteria, probiotics would be the live bacteria themselves, and postbiotics are inanimate bacteria or their components – which is much of what ‘probiotic’ creams actually contain. Postbiotics have a scientific definition: a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host. By that definition, pure filtrates without any cell components do not count. On packaging, though, the three terms are often used interchangeably, because ‘probiotic’ is the one people know best. Not every ingredient that comes from fermentation belongs to this family: fermented sugars such as Biosaccharide Gum-1 are used in cosmetics mainly as humectants and have nothing to do with the microbiome promise.

What do studies on probiotic skincare show so far?

So far, studies show that individual bacterial lysates can soothe sensitive skin in certain amounts, but not that microbiome skincare as a category does more than good basic care. A frequently cited example is a study in Experimental Dermatology: 66 women with reactive skin applied either a cream containing 10% of a Bifidobacterium longum lysate or a control cream twice a day for two months. In the extract group, sensitivity in the stinging test fell significantly, the skin coped better with physical and chemical stress, and after 29 days it was less dry, according to both the doctors’ assessment and the participants’ own.

This needs some context. The study was carried out by researchers from a large cosmetics group, it tests exactly one extract at exactly one concentration, and it measures skin sensitivity and barrier function, not the microbiome itself. Whether a cream that lists ‘Bifida Ferment Lysate’ far down its INCI contains anything like that amount is impossible to tell from the outside. The review in Molecules reaches a similarly sober conclusion: firm claims would need further strain-by-strain research and randomised trials in humans. In this field, then, promising means interesting for research, but not yet a reason to overhaul your routine.

What upsets the skin microbiome day to day, and what is gentle on it?

Your skin microbiome is most likely to be thrown off balance by the same things that put strain on the skin’s surface: cleansing too often and too harshly, using lots of products at once, constant exfoliating and fragrance on sensitive skin. That said, direct evidence in humans for each individual factor is thin. The reasoning goes via the habitat: if the skin’s acidity, lipids and moisture keep tipping out of balance, the conditions for the bacteria living on it change. A weakened barrier is usually the more visible part of the problem, and how to recognise a damaged skin barrier is a topic in its own right. With cleansing, what matters most is how mild it is and how often you do it – more on that in the article on what kind of cleanser your skin really needs. And if more products are making your skin more irritated rather than calmer, it is worth reading up on the signs that you are using too many products.

Conversely, the gentle option is a short routine with few irritants. That is exactly the idea behind The Duo serum and cream, although it is not probiotic skincare: it contains neither live bacteria nor bacterial lysates. Both products are fragrance-free and contain no essential oils. The Shield provides Ceramide NP, squalane and jojoba oil, and The Essential provides hyaluronic acid in three molecular sizes. In her review on Judge.me, Andrea G. writes: ‘My skin feels nourished and soft, but not overloaded’ (review translated from German).

How can you tell from the INCI whether microbiome skincare is more than a buzzword?

You can tell whether there is more to microbiome skincare than a buzzword from specific details: which bacterial ingredient, in what form, where it sits on the list and whether there is a study on exactly that ingredient. Without these details, terms such as ‘microbiome-friendly’ or ‘strengthens the skin flora’ tell you little. One labelling rule helps here: ingredients are listed in descending order of quantity, and only very small amounts may follow at the end in any order. Anything right at the end of the list is therefore usually present only in trace amounts.

1. Look for a bacterial ingredient: does the INCI include something like Lactobacillus Ferment, Bifida Ferment Lysate or Lactococcus Ferment Lysate? If not, ‘microbiome’ usually refers only to a test or a seal.
2. Check its position: far down the list means very little of it. That is not automatically bad, but it sits poorly with a big promise.
3. Be sceptical of ‘live cultures’ in a preserved, water-based cream.
4. Ask about the study: does the manufacturer state the number of participants, the duration and the concentration for exactly this extract?
5. Read the rest of the formula: fragrance, essential oils or alcohol near the top are an odd fit for a cream that presents itself as especially gentle. There is more on this in the guide to caring for sensitive skin.

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