Parabens, methyl, ethyl, propyl, benzyl, and butyl, are the most common preservatives in use today. They are the alkyl esters of p-hydroxybenzoic acid and are used extensively because they are relatively nonirritating and nontoxic and offer good antimicrobial coverage. Testing for paraben allergen can be done by patch testing. Two cases of allergic contact dermatitis (ACD) to parabens are used to discuss the background of parabens, their allergenicity, patch testing issues, and several "paraben paradoxes." Although ACD to parabens has been reported, given the widespread use, it is relatively uncommon. Because of their low rate of allergenicity and their favorable preservative profile and efficacy, parabens remain the number one preservative in use.