Preservatives

Any product that contains water, and most that are touched by fingers, needs a preservative. Without one, bacteria, yeasts and moulds can grow within weeks, spoiling the formula and risking infection of the skin or eyes. Preservatives are used in small amounts, often in combination, and are the reason a cream stays usable from the first day to the last. Phenoxyethanol, sodium benzoate, potassium sorbate and benzyl alcohol are among the most common you'll see on a label.

Phenoxyethanol, the most widely used, stops a broad range of microbes growing and is effective at 1% or less. Many formulas pair a preservative with 'boosters' such as ethylhexylglycerin, caprylyl glycol or 1,2-hexanediol, which let lower levels do the job. Parabens are among the most studied preservatives; the EU and UK ban some and set strict limits on the rest, and the US FDA says it has no evidence that parabens as used in cosmetics affect health. 'Preservative-free' products rely instead on airless packaging, single doses or ingredients with preserving properties.