This shift is particularly relevant to Cutibacterium acnes. Although C. acnes is a normal and abundant member of the skin microbiome, its presence alone does not explain acne. Research increasingly points to differences between C. acnes phylotypes, microbial diversity and interactions within the wider skin microbiome. [1]
For brands developing anti-acne cosmetics, this creates an opportunity to look beyond conventional antimicrobial testing and investigate microbial behaviour.
From bacterial reduction to microbial behaviour
Traditional antimicrobial testing can establish whether a cosmetic formulation reduces bacterial growth or viability. However, this does not necessarily explain how microorganisms communicate or behave as communities.
One area attracting increasing scientific interest is biofilm formation. Bacteria can form structured communities within a protective matrix, and research into C. acnes increasingly considers biofilm-associated behaviour as part of the complex microbiology of acne.
This has implications for anti-acne cosmetic testing. Rather than focusing exclusively on eliminating C. acnes, cosmetic research can also investigate whether specific microbial behaviours can be influenced.
One emerging approach is Quorum Sensing.
What is Quorum Sensing?
Quorum Sensing is a bacterial communication mechanism through which microorganisms use signalling molecules to coordinate certain behaviours at the community level. These behaviours can include functions associated with biofilm formation and other microbial characteristics.
Quorum Quenching refers to approaches designed to interfere with these communication processes.
For cosmetic research, this opens an interesting alternative to broad antimicrobial strategies: investigating whether an ingredient or formulation can influence bacterial communication and associated behaviours without relying solely on bacterial elimination.
Recent research has further highlighted the relevance of this area. Kupke et al. investigated C. acnes and Staphylococcus epidermidis in multispecies systems, examining their interactions alongside quorum-sensing activity, biofilm characteristics and the potential quorum-sensing inhibitory effects of Plectranthus aliciae. [2]
While such findings do not automatically translate into cosmetic efficacy claims, they demonstrate the growing scientific interest in quorum sensing and quorum quenching as areas for further investigation.
Quorum Quenching analysis for cosmetics
At QACS, a cosmetic testing leader with expertise in microbiology, molecular biology and cosmetic efficacy testing, we have developed Quorum Quenching Analysis (QQA) as an additional tool for investigating microbial mechanisms relevant to cosmetic development.
Quorum Quenching Analysis can be used to investigate the potential of cosmetic ingredients and formulations to interfere with bacterial communication under controlled in vitro conditions.
For cosmetic developers, QQA can complement Cutibacterium acnes testing, antimicrobial testing, biofilm testing and broader cosmetic microbiome testing. This creates the possibility of evaluating several aspects of a formulation's microbiological profile rather than relying on a single endpoint.
For example, QQA can form part of an early-stage testing strategy when screening candidate ingredients or formulations, helping identify those with promising quorum-quenching activity for further investigation. The value is therefore not simply in determining whether bacteria are reduced, but in exploring how bacterial behaviour may be influenced.
The next generation of anti-acne cosmetic testing
The evolution of microbiome science is encouraging a broader rethink of how cosmetic products for acne-prone skin are evaluated. For Cutibacterium acnes cosmetics, the question is increasingly moving beyond “does the product reduce bacteria?” towards a more nuanced understanding of microbial balance, interactions and behaviour.
This does not make conventional antimicrobial testing less relevant. Instead, it creates an opportunity to combine established methods with emerging approaches such as Quorum Quenching Analysis.
As a cosmetic testing leader, QACS supports brands in translating emerging microbiome research into practical laboratory testing strategies, helping cosmetic developers investigate innovative mechanisms of action and build stronger scientific foundations for product development.
The future of anti-acne cosmetic testing may therefore be less about eliminating microorganisms indiscriminately and more about understanding the microbial ecosystem — and investigating whether specific behaviours can be selectively influenced.
Scientific references
- Dréno B, Dekio I, Baldwin H, Demessant AL, Dagnelie M-A, Khammari A, Corvec S. Acne microbiome: From phyla to phylotypes. Journal of the European Academy of Dermatology and Venereology. 2024;38(4):657–664. doi:10.1111/jdv.19540.
- Kupke IA, Spittaels K-J, Coenye T, Lall N. Anti-quorum-sensing activity of Plectranthus aliciae in multispecies Cutibacterium acnes-Staphylococcus epidermidis systems. Phytomedicine. 2026;156:158260. doi:10.1016/j.phymed.2026.158260.
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