For years, acne cosmetic testing has focused on whether a product can reduce Cutibacterium acnes.Emerging microbiome research suggests that the answer may be more complex.
C. acnes is a normal member of healthy skin microbiota, so its presence alone does not explain acne. Increasing evidence points to differences between bacterial strains and, importantly, how they behave. Certain C. acnes groups associated with acne show greater inflammatory activity and a stronger tendency to form biofilms than groups more commonly found on healthy skin [1].
A biofilm is a structured community of bacteria surrounded by a protective matrix. In this state, C. acnes can become more persistent and more tolerant to antimicrobial activity and host defences [1]. This raises an important question for cosmetic development: rather than simply eliminating bacteria, can products influence the behaviours associated with acne?
One emerging approach is quorum sensing, the communication system bacteria use to coordinate collective behaviours, including biofilm formation. Recent research in multispecies C. acnes–Staphylococcus epidermidis models has demonstrated enhanced biofilm-related activity and investigated the potential of plant-derived compounds to interfere with quorum sensing [2].
For cosmetic developers, this opens a new perspective on acne and microbiome testing. QACS, a specialized cosmetic testing laboratory, brings this functional approach into product development through its Quorum Quenching Analysis. The analysis is designed to investigate whether cosmetic ingredients and formulations can interfere with bacterial communication and reduce biofilm development, providing data on mechanisms beyond conventional antimicrobial testing.
By adding Quorum Quenching Analysis to cosmetic testing strategies, brands can explore more targeted approaches to acne-prone skin and develop microbiome-focused products supported by scientific evidence. For QACS, this represents the next step in cosmetic microbiome testing: moving from measuring bacterial presence alone toward understanding and evaluating bacterial behaviour.
[1] Dréno et al., 2024
[2] Kupke et al., 2026
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