In order to avoid microbial contamination and assure the shelf life of cosmetics, active antimicrobial ingredients such as parabens are added to formulations. The success of these widely used preservatives is mostly due to their ease of use and low cost. However, in recent years, as many scientists worldwide have researched the effects of parabens on humans, some studies have suggested that parabens exhibit estrogenic activity, or have found them in human breast tissues.1, 2 This has led to criticism over their presence in skin care products, so in response to consumer fears, formulators have replaced parabens with alternative preservative systems or preservative-free “hurdle” technologies.3, 4 Such technologies often contain natural preservatives or ingredients with antimicrobial properties that are not registered as preservatives. Despite the controversy surrounding parabens, however, they are still present in most cosmetics. Therefore, assessing the skin delivery and penetration of parabens is crucial to estimating their potential risk because they cross the cutaneous barrier and enter the systemic circulation. In this article, percutaneous penetration studies of parabens spanning the past 20 years are reviewed to determine how a number of parameters affect paraben penetration and to assess the risk of various preservative classes as they are formulated into cosmetics.