Q&A: Microbiome-friendly beauty and personal care: testing, products and ingredients

Back in August 2020, we spoke with Dr Kristin Neumann, author and founder of MyMicrobiome – a biotechnology company that scientifically tests and certifies products as ‘microbiome-friendly’. Dr Neumann got us up to speed on what makes a product microbiome friendly, and how we know if is really safe for our microbiome (see article here).

Since then, skin-microbiome-related beauty and personal care has continued to grow and evolve. With many product launches across this space over the past two years, we thought it would be good to check in with Dr Neumann again to get the latest on microbiome-friendly testing…

Overview of the industry and microbiome-friendly products

Is there an interest in microbiome-friendly products amongst industry and consumers, and do you think this has grown since we last spoke? Do you think the space or market has evolved in any way?

Interest is definitely there – a recent internal survey has shown that 20% of respondents see microbiome-friendly certified ingredients as the biggest microbiome opportunity in terms of ingredients, and well-known brands such as Dove, Vaseline and Persil have products with microbiome-related claims. This is because consumers are clearly seeking products that respect the balance of the skin microbiota. According to Mintel in 2019, for example, 50% of consumers of soap/bath/shower products aged 18+ years in the US were interested in trying products that protect the microbiome.

In terms of growth, it is hard to get a precise view of how consumer interest is increasing or evolving when it comes to the microbiome. But it does fit with the growing popularity of a more holistic and conscious approach to health – with individuals focusing on a healthy lifestyle, rather than a dependency on pharma products. Understanding of the microbiome also needs to catch up in some areas such as Germany, and here having microbiome-friendly products on the shelf will help consumer curiosity grow and help educate.  

What exactly are the challenges faced by beauty and personal care product developers in relation to the skin microbiome?

The way that skin reacts to hormones and to C. acnes proliferation depends on an individual’s genetics,

Microbiome-related pain points for developers in this industry include, for example:

(1) Linking a change in the microbiome to an observable benefit, and being able to make a claim about this.

(2) Regulatory guidance and use of the right terminology.

(3) Formulation challenges – how to formulate products for the microbiome. The terms pro-, pre- and postbiotics are very popular but in most cases these types of ingredients don´t make sense in cosmetic products when formulating products for the microbiome. Anyway, it is a challenge to formulate with live bacteria (e.g. maintaining vitality, and ensuring no contamination, despite not using preservatives). Keeping the balance between safety and microbiome-friendliness of a product is a task I often see with our customers.

(4) Scientific education among customers and consumers.

Since the last interview, have there been any notable changes or challenges when it comes to microbiome-friendly testing and related claims?

The most notable challenge remains the lack of standardization in the field – particularly when testing products in vivo. In vitro tests are more standardizable and can be used for certification of products. However, since the cosmetics industry is used to work using in vivo models, beauty and personal care developers are still trying to use in vivo tests to answer specific questions, even though we know the outcomes are in most cases not meaningful.

There is also an issue surrounding product regulation and interaction with regulatory authorities. This results from a lack of understanding due to the complexity of the topic. As always, the industry is working ahead of the science. We still need to learn so much.

Testing specifics

Can you tell us more about the service that MyMicrobiome offer to its customers?

We focus on testing products to establish the impact they have on the microbiome.
In the lab, we cultivate microbial populations that we know are present in specific body areas – growing the populations either in liquid (which allows the microbial populations to interact) and on agar dishes (which allows direct and indirect testing of products).

Using this set up, we can carry out various tests to establish whether a product is microbiome friendly.

How do you define a microbiome-friendly product or ingredient? What qualities does an ingredient or product need to be certified as microbiome-friendly?

Cosmetic ingredients and products should not lead to a disbalance of the skin microbiota – they should not significantly modify the natural distribution of the commensal skin microbes, or (over)stimulate the growth of microbes.

So the main underlying principle is that products or ingredients should have no influence on the key players of the microbiome. The ingredients and products need to be safe – for example, not bearing harmful bacteria, and should respect the resident microbes or our skin microbiome.

How do you assess this?

We look at four key criteria to make this assessment:

(1) Microbial quality

(2) Balance

(3) Diversity

(4) Vitality – direct and indirect

What precise testing or methods do you use?

Using the liquid, plate or agar cultures, we can carry out a diverse array of tests.

Balance tests, for example, involve adding a product and observing the impact on the ratio between populations of ‘good’ and ‘bad’ microbes – the measurement of which can be used as an indication of product safety. Then we have diversity testing – here we are looking at the interaction between the key microbes of the respective body area in the co-culture. We use liquid culture for this testing as this allows interaction, as opposed to plate or agar cultures, and we can then add a product and measure how it impacts the co-culture compared to a control. 

Directing testing involves the application of the product directly to a plate with a microbe culture to see the result, whereas indirect testing involves the application of the product onto agar, with the microbial population below, which more accurately mimics the diffusion of the product into the environment of the deeper skin layers.

By performing multiple test types, we can build an overall picture of the whole performance and safety of the product for the human microbiome.

Can you tell us about the pros and cons of in vivo versus in vitro testing, or maybe situations where you would use one versus the other?

The choice between in vitro and in vivo depends on what you are testing for.

If you look at a very specific end point, such as reduction of Staphylococcus aureus in eczema skin, it is possible to see this in vivo. However, investigating influence of a product on the healthy skin microbiome remains a challenge when testing in vivo. There is no standard ‘healthy microbiome’ , as there is so much variation between individuals and the microbiome underlies manifold influences. This means that it is hard to say for certain whether a product significantly improves or harms the microbiome in vivo. 

In vitro is standardized and controllable. By culturing and testing on a distinct set of microbes that we know is representative of resident microbes on human skin, we can precisely identify the effect of a product on the microbes. This can allow us to see changes in diversity and abundance ratios, and the effect on microbes that are, for example, known to be pathogenic.

What problems can products introduce to skin if not tested appropriately to ensure microbiome friendliness?

If we look at soap, for example, products often remove:


(1) The skin sebum, which acts as a nutrient for microbes
(2) Skin lipids, which are key to the health and functioning of the skin barrier
(3) Resident bacteria, disrupting the natural skin microbiome composition

Products can also disrupt skin pH, irritating the skin barrier and microbial balance.

When it comes to cosmetics – they often contain preservatives and other antibacterial actives, essential oils, surfactants, alcohol and fragrances that can irritate the skin and its microbiome. Products used daily also accumulate, with residues of some products found on the skin weeks after use.

Molecular and bacterial temporal variability is product-, site- and person-specific, but these effects mean that beauty and personal care end-products can alter molecular and bacterial diversity, as well as the dynamic and structure of molecules and bacteria on our skin.

Are there any specific skin types that require special testing? For example, skin site, skin conditions or age differences?

We use different microbial cultures for different body sites. For example, for the vaginal microbiome, the focus is on Lactobacillus and Gardnerella for balance tests as these are the dominant or often pathogenic bacteria in this area on the human body.

We then have a specific testing protocol for infant skin, as the microbiome of young skin differs to that of adults. However, from puberty onwards, the skin microbiome remains relatively stable.

We are also working to develop a standardized testing regime for skin conditions such as acne or eczema, as there are specific bacterial species and strains to consider here. However, we haven´t yet found the right products that would meet the criteria for these standards.

Recommendations and future outlook for developers

Are there any specific ingredients/products or formulation types that require special consideration, or are particularly challenging?

In the lab, it can be difficult to work with waxes and solid products, but we manage to do so. We see strong effects with surfactants, so microbiome-friendly shampoos and shower gels are hard to find. Mineral sunscreen can be problematic when testing for microbiome friendliness. Products for acne- or eczema-prone skin also have to undergo specific testing, as they should be preserving or eradicating specific bacterial species or strains (for example, specific Cutibacterium acnes strains in the case of acne products).

When it comes to formulation, we often work along with our customers to improve the formulations to be optimal for the human microbiome. In the end, microbiome-friendly products are often more expensive than average products which often make poor ingredient and preservative choices to keep costs down and extend shelf life.

How can developers design or formulate their products to be as microbiome friendly as possible from the get-go?

There a few tips to consider during the development process:  


(1) Formulating with surfactants – avoid sulfate-based surfactants, and make use of amino-acid, isethionate, glucoside-derived or betaines-based surfactants.

(2) Formulating with preservative systems – avoid traditional biocidal preservatives, and make use of bacteriostatic agents and preservative boosters that are multifunctional (alkane diols, ethylhexyl glycerin and glycols).

(3) Using active ingredients that strengthen the skin barrier – such as vitamin B3, hyaluronic acid and saccharide isomerate – these can help reduce TEWL and replenish intracellular lipids (linoleic, oleic, palmitic acids and ceramides) to help reduce irritation, protect and boost the skin immune system and inhibit inflammatory responses.

(4) Optimize synergies between ingredients – for example, use of anti-oxidants with chelating agents. However, the association of different ingredients cannot always be predicted – this requires a case-by-case optimization process.

Will greater understanding of the microbiome potentially prohibit some products from being sold?

Perhaps in the long term, but regulation is very slow-moving. The current consensus is that as long as a product does not have a tangible, severe effect on health, it is unlikely that the FDA or other regulatory bodies will take action at present.

However, in the long term, it is important to work with regulatory boards. The microbiome field is so new, it could lead to regulations that inhibit certain ingredients that create imbalances in the human microbiota. An example here is the effect of cosmetics and personal care products over time – the effect of long-term use and application of several products is hard to measure, as it means measuring the impact of different products on the microbiome in vivo over multiple years. 

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