Propyl paraben is the benzoate ester that is the propyl ester of 4-hydroxybenzoic acid. It is typically used as a preservative in many water based cosmetics, such as creams, lotions, shampoos, and bath products. It can also be used as a food additive. Propyl paraben prevents the growth of mold and other harmful bacteria. It has a role as an anti-fungal agent as well as an anti-microbial agent.