SKIN MICROBIOME 37


proportion of organic ingredients, and Cosmos Natural, prioritizing natural ingredients without a minimum organic threshold. Certified products must contain at least 95%


natural ingredients, strictly exclude controversial substances such as pesticides, phthalates, parabens, and phenoxyethanol, and adhere to eco-friendly packaging and controlled manufacturing processes. While Cosmos certification does not mandate


direct microbiome testing, its strict formulation restrictions align with scientific evidence suggesting reduced risk of dysbiosis. Avoidance of harsh preservatives, surfactants,


and petrochemicals is particularly relevant because conventional cosmetic preservatives and detergents have been shown to disrupt microbial diversity and reduce commensal populations.26,23 Parabens, phenoxyethanol, and aggressive


sulfates, for instance, can perturb resident skin bacteria, favouring opportunistic pathogen overgrowth. Additionally, exposure to petrochemical


leachables such as phthalates or residues from raw materials can alter microbial physiology, biofilm formation, and commensals’ stability, emphasizing the importance of minimally processed and ‘clean’ formulations.27,28 These findings are highly relevant to cosmetics,


as they underscore the microbiome risks posed by synthetic additives and leachables. COSMOS certification, by restricting phthalates, petrochemicals, and toxic processing residues, indirectly supports skin microbiota resilience by reducing exposure to compounds that may disturb commensal–pathogen dynamics.29,28,23 COSMOS also encourages the use of natural


oils, waxes, and polysaccharides, which reinforce the skin lipid barrier and provide substrates for beneficial microbes. Prebiotic cosmetic actives nourish commensal bacteria and stabilize


microbial communities, supporting diversity and homeostasis.29 Prebiotic ingredients, combined with mild


surfactants (e.g. glucosides) and eco-approved preservatives such as potassium sorbate or sodium benzoate, contribute to formulations that are less disruptive to the microbiome.28,23 Mechanistic evidence further supports the


importance of minimizing synthetic residues for microbial health. Mass spectrometry and microbiome sequencing studies have shown that topical products leave chemical signatures on the skin that correlate with measurable shifts in microbial composition. These chemical changes persist for hours or days. Certain microbial polulations increase while


others decrease after exposure to conventional formulations. Therefore, reducing residual synthetic chemicals is expected to help maintain or restore microbial equilibrium.30 Topical products can significantly alter skin


chemistry and microbiome composition, with effects varying by formulation type. Murphy et al28


showed that common preservative


systems in cosmetic formulations can reduce microbial diversity in vivo. Pinto et al23


confirmed


that preservatives such as parabens and phenoxyethanol disrupt resident microflora. Conversely, microbiome-friendly formulations


incorporating natural actives and mild preservatives have been shown to support microbial resilience.31


It has further emphasized


the potential of microbiome cosmetics, particularly those aligned with natural certification standards, to maintain skin health through microbial balance.32 While certified products are less likely to


disrupt microbial communities, their direct effects depend on formulation specifics. Cosmos-certified cosmetics, by virtue of their ingredient restrictions


and sustainability criteria, are generally more compatible with the skin microbiota than conventional formulations. They reduce exposure to harsh preservatives


and surfactants, support barrier integrity, and increasingly incorporate microbiome-friendly actives. However, while Cosmos certification increases the likelihood of microbiome compatibility, formulation specifics and clinical validation remain critical to establishing concrete effects on microbial homeostasis.


Conclusion The skin microbiome represents a remarkably diverse and dynamic ecosystem, composed of bacteria, fungi, viruses, and archaea, which is fundamentally crucial for maintaining cutaneous homeostasis. The resident flora provides essential protection


through competitive exclusion and the synthesis of beneficial compounds, including bacteriocins and short-chain fatty acids, which modulate the skin’s pH and immune tolerance. The composition of this flora is dictated


by a complex interaction between intrinsic physiological factors (such as host genetics, pH, and lipid composition) and numerous extrinsic factors (including climate, diet, hygiene, lifestyle and cosmetics). A disruption of this essential equilibrium,


known as dysbiosis, is a consistent clinical feature in inflammatory dermatoses such as atopic dermatitis and Acne vulgaris. In this context, cosmetic products play a pivotal role, as their formulation architecture, ingredients, and preservatives constantly interact with the skin’s physicochemical environment. Moving beyond formulations that are merely


non-disruptive, microbiome-supportive strategies such as utilizing prebiotics, postbiotics, barrier


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March 2026 PERSONAL CARE MAGAZINE


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