The relative cytotoxicity of personal care preservative systems in Balb/C 3T3 clone A31 embryonic mouse cells and the effect of selected preservative systems upon the toxicity of a standard rinse-off formulation

Abstract: Biocide chemicals are commonly used as preservatives for cosmetic and personal care products and the conditions for their use are stipulated in Annex VI of the Cosmetics Directive. In these studies the cytotoxicity (EC50 and EC90) of a range of preservatives including the isothiazolinone family, formaldehyde donors, parabens mixtures and organic acids have been established in the Balb/C 3T3 clone A31 fibroblast cell-line following a 1h exposure. Cell viability was established using the neutral red uptake assay 24h after exposure. The potency of the preservatives spanned several orders of magnitude from the isothiazolinones (EC50<10ppm) to the organic acids (EC50>10000ppm). Although these values are directly proportional to the anti-microbial efficacy of the actives, they do not reflect the addition levels commonly used to preserve formulations, which are intended to provide prolonged protection against a wide spectrum of spoilage organisms. In a further study, the cytotoxic profile of an unpreserved standard rinse-off body wash formulation was assessed. Two concentrations of the formulation were selected: 0.1% v/v (EC98) and 0.15% v/v (EC82) to study the effects of selected preservative chemicals at recommended addition levels upon the cytotoxicity of the formulation. At 0.1%, only preservation with benzoate/sorbate at the highest addition level increased the toxicity, whereas at 0.15%, preservation with 2-bromo-2-nitro-propane-1,3-diol increased the cytotoxicity of the formulation. No other preservatives, including isothiazolinones and formaldehyde donors affected the basal cytotoxicity of the formulation. Theses studies have provided a standardised assessment of the cytotoxicity of cosmetic preservatives and demonstrated that preservation of a rinse-off formulation at recommended addition levels is unlikely to affect the cytotoxic profile. [Copyright &y& Elsevier]