This was according to researchers from Shanghai-based chemistry and biotech firm Henning Chemical.
Cosmetic preservatives play a crucial role in ensuring product safety and shelf life, as they prevent microbial contamination and spoilage. Recent research into preservative mechanisms has shed light on how these substances protect products while addressing consumer demand for safer, more sustainable options.
Based on this, researchers at Henning Chemical conducted a review in order to provide an overview of the current understanding of the anti-microbial mechanism of action of preservatives used in cosmetics.
Cosmetics provide an ideal environment for bacterial and fungal growth. Without preservatives, these products could quickly become unsafe for use, potentially causing skin infections or irritations. Preservatives not only extend the shelf life of cosmetics but also ensure safety during prolonged use.
Different preservative types — ranging from synthetic chemicals to natural alternatives — cater to the varied needs of the cosmetics industry. However, growing consumer concerns about potential health risks and environmental impact are driving innovation toward ‘clean and green’ formulations.
Synthetic preservatives: Proven efficacy amid increasing scrutiny
Synthetic preservatives such as parabens, isothiazolinones, and phenolic compounds have long been staples in the cosmetics industry. These ingredients are effective in preventing microbial growth across a broad spectrum of organisms.
Parabens like methylparaben and butylparaben, for instance, disrupt microbial cell membranes and metabolic processes. Despite their efficacy, regulatory bodies like the European Commission have limited their use due to concerns about endocrine disruption and bio-accumulation.
At the same time, methylisothiazolinone (MIT) and its variants act by inhibiting microbial enzyme activity and inducing oxidative stress. Regulatory frameworks have tightened restrictions on their concentrations due to rising cases of skin sensitisation.
Additionally, phenolic compounds like phenoxyethanol disrupt microbial membranes and inhibit DNA synthesis. While phenoxyethanol is widely accepted for its safety at regulated concentrations, it often requires combination with other agents for broader protection.
Evolving preferences for natural alternatives
Natural preservatives, including essential oils, plant extracts, and anti-microbial peptides (AMPs), are gaining traction due to consumer preference for sustainable, minimally processed products. These ingredients provide anti-microbial benefits while reducing sensitisation or toxicity risk.
Compounds such as thymol and eugenol, for instance, demonstrate broad-spectrum anti-microbial properties. Their ability to disrupt microbial membranes and interfere with metabolic pathways makes them viable alternatives to synthetic options.
Flavonoids and phenolic compounds found in sources like tea polyphenols exhibit antimicrobial activity by increasing bacterial cell membrane permeability. However, variability in composition and effectiveness remains a challenge.
Furthermore, naturally occurring AMPs like nisin offer promising preservative potential by disrupting bacterial membranes. Their broad-spectrum activity makes them suitable for diverse formulations.
Multi-functional ingredients and boosters
Innovative approaches to preservation now include multifunctional ingredients like alkanediols and caprylhydroxamic acid. They not only provide antimicrobial protection but also deliver secondary benefits such as moisturizing and stabilizing properties.
For example, caprylhydroxamic acid (CHA) can chelate iron, allowing it to limit microbial growth by restricting essential nutrients. Its effectiveness across a wide pH range enhances its appeal in sensitive skin formulations. In addition, alkanediols such as 1,2-hexanediol and caprylyl glycol disrupt microbial membranes while improving product texture and hydration.
Regulatory landscape and industry implications
The cosmetics industry operates under stringent regulations worldwide, with entities like the European Union (EU) and China enforcing strict limits on preservative concentrations. For example, isothiazolinones are capped at 0.0015% in rinse-off products under EU law, while parabens are limited to 0.4% for single esters.
Although formaldehyde releasers like DMDM Hydantoin and halogenated preservatives such as bronopol offer robust antimicrobial effects, they face increasing regulatory scrutiny. Formaldehyde’s association with carcinogenic risks and sensitisation has prompted manufacturers to seek safer alternatives. For example, the EU mandates that formaldehyde releasers be labelled appropriately if concentrations exceed specific thresholds.
Navigating these regulatory landscapes requires manufacturers to balance efficacy, safety, and consumer preferences. Increased transparency in ingredient-sourcing and labelling has become essential for regulatory compliance, as well as maintaining consumer trust.
Future directions: Towards safer, more sustainable preservation
Research into the mechanisms of preservatives is advancing the development of safer and more effective ingredients. Key areas of focus include mechanistic insights, which involve understanding how preservatives interact with microbial cells.
Another focus area is combination strategies, which entail blending natural and synthetic preservatives to enhance antimicrobial action while addressing safety concerns. Researchers are also looking into emerging technologies, including advanced tools like omics techniques that are helping scientists uncover novel preservation methods and optimise existing ones.
As consumer demand for “free from” claims grows, the cosmetics industry is likely to prioritise natural, multi-functional preservatives. The shift aligns with a broader trend towards sustainability and health-conscious product development.
Preservatives remain integral to ensuring the safety and longevity of cosmetic products. By deepening scientific understanding and embracing innovation, the industry can address regulatory challenges and meet evolving consumer expectations. This dynamic environment presents opportunities for manufacturers to differentiate themselves through safer, more sustainable formulations.
Source: Journal of Dermatologic Science and Cosmetic Technology
“Mechanism of action of preservatives in cosmetics”
https://doi.org/10.1016/j.jdsct.2024.100054
Authors: Tang Zhenyu, et al.