Bottle of Eucerin Probiom8 TopiC.A beside a microscope

The Science Behind Probiotic Treatment
FOR ACNE-PRONE SKIN

Read Time

4 min

In short:

CA-IA1 dominates the skin microbiome?
PREBIOTICS, PROBIOTICS AND POSTBIOTICS IN SKINCARE
TOPIC.AThe probiotic science behind Probiom8
How TopiC.A powers thePROBIOM8 ROUTINE
Frequently asked questions about the science behind Probiom8
WHAT'S NEXT?

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Blemishes have long been treated as a surface problem. But the real story starts much deeper, in the microbiome of the skin. The trillions of microorganisms that make up the skin microbiome play a critical role in keeping skin healthy. When that balance is disrupted, the conditions for blemishes are set in motion – and it starts with one bacterium.

What is C. Acnes
what role does it play?

The skin is home to a vast ecosystem of bacteria, fungi and other microorganisms – the skin microbiome. This microbiota of the skin is as unique as a fingerprint: no two people share exactly the same microbial community.

The most abundant bacterium on the face is Cutibacterium acnes, commonly known as C. acnes. It is a natural and permanent resident of healthy skin. In a healthy skin microbiome, C. acnes bacteria helps support a healthy skin barrier and protects against inflammation. But when its balance becomes disrupted, it can contribute to acne and other skin concerns.

Learn more about the skin microbiome

Close-up of inflamed acne blemishes on skin before using the Eucerin Probiom8 Kit

Close-up of a woman with facial blemishes touching her chin

The six faces of C. acnes

Science has identified six distinct types of the C. acnes bacteria: CA-IA1, CA-IA2, CA-IB, CA-IC, CA-II and CA-III. These six types were identified using advanced phylogenetics technology in the 2000s, built on Beiersdorf's pioneering research dating back to 1894, when Professor Dr. Unna first identified the bacterium.

All six C. acnes types are present in every skin. In healthy skin, they coexist in balance. In acne-prone skin, this balance breaks down: Acne-associated C. acnes begin to overpopulate, while the others are suppressed. This imbalance is a driving cause of blemishes. (Hamann et al. 2025)

What happens when

CA-IA1 dominates the skin microbiome?

When acne-associated C. acnes dominates the skin microbiome, it triggers a chain reaction:

Excess sebum production
Bacterial overgrowth
Hyperkeratinisation (thickening of the skin that blocks pores)
Inflammation
Visible pimples and breakouts

PREBIOTICS, PROBIOTICS AND POSTBIOTICS IN SKINCARE

Microbiome science has identified three types of ingredient that can affect the skin microbiome: prebiotics, postbiotics and probiotics. While prebiotics and postbiotics can support and soothe it, only probiotics can actively restore the C. acnes balance. Here is what each one does:

Prebiotics
Prebiotics are nutrients that feed the bacteria already present on the skin's surface. Think of them as fertiliser: they help what is already there to thrive. Prebiotic skincare can support the microbiome in general, but because they feed all bacteria they cannot restore a disrupted balance on their own.

Postbiotics
Postbiotics are beneficial compounds produced by bacteria as by-products – things like short-chain fatty acids and enzymes. Postbiotics in skincare can help soothe and calm the skin, and may support the skin barrier. Like prebiotics, however, they work with what is already on the skin. Postbiotics skincare products cannot replenish bacterial strains that are missing from the microbiome.

Probiotics
Skin-native probiotics are live, beneficial bacteria. They are the only ingredient category that can actively introduce new bacterial strains to the skin's ecosystem. When applied topically, probiotics can integrate into the existing skin microbiome, helping to replenish beneficial strains and shift the microbial balance back toward a healthier state.

TOPIC.A
The probiotic science behind Probiom8

TopiC.A is the result of over 20 years of microbiome research, 30 scientists and 9 patents pending. It is the world's first skin-native probiotic technology designed specifically for acne-prone skin. CA-31 and CA-81, its two active probiotic strains, were discovered and isolated from healthy human skin – working in harmony with the skin's existing biology and capable of modulating the skin microbiome.

Two regulators.
One precise approach.

CA-31 and CA-81 are not identical in their action, and that is by design. Together, they provide a two-speed, complementary approach to C. acnes treatment, targeting the overpopulation of CA-IA1 with both immediate and lasting action.

Illustration of CA-31 probiotic for fast regulation of acne-associated C. acnes

CA-31

Illustration of CA-81 probiotic for sustained microbiome support used in Eucerin Probiom8 kit

CA-81

Eucerin Probiom8 TopiC.A drops being dispensed into the hand before mixing with moisturizer

50 million skin-native bacteria
in one drop

In a single drop, TopiC.A delivers up to 50 million skin-native probiotics to the skin, enough to begin restoring the skin microbiome balance from the very first application. Managing living bacteria in a stable skincare formula was considered nearly impossible. The Eucerin research team made it a reality.

How TopiC.A powers the
PROBIOM8 ROUTINE

TopiC.A is integrated into the Probiom8 8-week routine – a complete skincare system for acne-prone skin, used morning and evening to improve skin microbiome balance. In clinical studies on more than 3,000 patients, the routine delivered a 68% reduction in pimples across 8 signs after 8 weeks.*

See the full clinical results

^{* Clinical Study, Brazil 2023, lesion count, reduction of papules, median based on the 33% of subjects with the highest reduction compared to baseline, after 8 weeks}

Woman's face with infographic: 8 signs of acne corrected: post-acne marks, pores, redness, oiliness, skin discomfort, mental discomfort and red and white pimples

Discover the Probiom8 routine

Frequently asked questions
about the science behind Probiom8

The science behind microbiome-based treatment for acne-prone skin is genuinely new and it raises real questions. Below, we've answered the five most common ones so you can understand exactly how and why Probiom8 works the way it does.

The skin microbiome, the community of microorganisms living on the skin, plays a central role in acne-prone skin development. In a healthy skin microbiome, six different types of C. acnes bacteria coexist in a balanced state, each keeping the others in check.

In acne-prone skin, this balance can break down, with acne-associated phylotypes such as CA-IA1 C. acnes becoming overrepresented, while overall strain diversity of the skin microbiome decreases. This microbial imbalance triggers inflammation, excess sebum, blocked pores and the visible breakout cycle. It is not simply having C. acnes on the skin – it is the imbalance of the microbiota of the skin that creates the conditions for blemishes to form. (Hamann et al., 2025)

C. acnes, short for Cutibacterium acnes, is the most abundant bacterium found on the face microbiome and a natural part of the human skin microbiome. On its own, it is not harmful. In fact, it plays an important role in maintaining a healthy skin environment.

The C. acnes bacteria exists in six distinct types. When all six coexist in balance, the skin remains healthy. When one type (CA-IA1) acne-associated C. acnes overpopulate, as happens in acne-prone skin, it disrupts the skin's microbial equilibrium and triggers the inflammatory processes that lead to visible blemishes. Beiersdorf first identified C. acnes in 1894; the six distinct subtypes were characterised in the 2000s using modern phylogenetics technology.

These three ingredients are often grouped together, but they work in fundamentally different ways:

Prebiotic skincare provides nutrients that feed the beneficial bacteria already living on the skin. Prebiotics support the existing microbial community, but because they nourish all bacteria equally, they cannot selectively restore missing beneficial strains.

Postbiotics in skincare deliver beneficial compounds produced by bacteria, such as enzymes and fatty acids. Postbiotics can help calm and soothe the skin, but like prebiotics, they work with what is already present and cannot replenish absent strains.

skin-native probiotics are live, beneficial bacteria. They are the only ingredient that can actively introduce new bacterial strains to the skin's ecosystem, which is why they are the only approach capable of truly restoring skin microbiome balance in acne-prone skin.

Yes, and the scientific evidence supporting this is growing rapidly, with over 187,000 related publications now available on PubMed. Probiotics are the only skincare ingredient capable of actively replenishing the beneficial bacterial strains that are missing or suppressed in acne-prone skin.

When skin-native probiotic strains are applied topically, they can integrate into the existing microbial ecosystem and begin to balance the skin microbiome by limiting the overpopulation of CA-IA1 acne-associated C. acnes. This addresses blemishes at their actual biological root, the microbial imbalance, rather than managing visible signs alone.

Not all probiotics are equally effective for this purpose, however. The strains used must be selected specifically for their interaction with C. acnes and their ability to survive in a topical skincare formula and engraft on the skin. That is precisely what makes TopiC.A, with its skin-native CA-31 and CA-81 strains, a scientific breakthrough.

TopiC.A is the probiotic technology at the core of the Probiom8 routine. It contains two skin-native probiotic strains, CA-31 and CA-81, that were isolated directly from healthy human skin. Because they are native to the skin's own biology, they integrate naturally into the existing skin microbiome.

CA-31 acts as a fast regulator, quickly targeting the overpopulation of CA-IA1. CA-81 acts as a slow regulator, delivering sustained microbiome support over time. Together, they provide a dual-action approach to C. acnes treatment that is both immediate and long-lasting.

In a single drop, TopiC.A delivers up to 50 million skin-native probiotics directly to the skin. Integrated into the complete Probiom8 8-week routine, this high-precision microbiome technology is what makes the routine's clinical results, including a 68% reduction in pimples in over 3,000 patients, possible.

WHAT'S NEXT?

Bottle of Eucerin Probiom8 TopiC.A beside a microscope

Man applying Eucerin Probiom8 product to blemished, acne-prone skin

Dr Emma Amoafo, Eucerin consultant dermatologist

Dermatologist Advice

Woman with mild blemishes on acne-prone skin

Probiom8