*2.1.4.2 Preservatives*

Preservatives are essential components of water-based topical moisturiser formulations and skincare products in general, as they protect products from potentially harmful bacteria. Without preservatives, water-based products would have a very short shelf life and would, for the most part, have to be stored at lower temperatures [59, 60]. Parabens such as methyparaben and propylparaben are arguably the most commonly used preservative ingredients. They have antimicrobial efficacy against a broad spectrum of yeasts, moulds and bacteria, although they are most effective against gram-positive organisms such as *S. aureus* [61]. While parabens exact mechanism of action is not well understood, it is thought to involve the disruption of a pathogen's cell membrane transport processes [62] and the inhibition of DNA/RNA synthesis [63] but it is generally believed that their inhibitory effects on membrane transport and mitochondrial functional processes are key to their antimicrobial actions [64]. The popularity of parabens is based on several advantages when compared to alternative preservatives, including their broad spectrum of antimicrobial activity, stability over a wide temperature and pH range, low degree of systemic toxicity, low frequency of sensitisation, sufficient water solubility, well documented safety record and their lack of odour, taste or colour [59, 60].
