DeCusatis, Cara MariaWhile there is considerable research on the topic of trust when it comes to health information or news media, there is less work examining how trust and expertise are conceptualized for information that may straddle both subjective and objective approaches to knowledge. In this thesis, I use the subreddit r/SkincareAddiction as a field site to examine how users construct skincare expertise and position skincare expertise in relation to formalized bioscience and experiential knowledge. Building on Science and Technology Studies’ theories of lay expertise and embodiment, I investigate how users interpret, share, and enact skincare and subreddit competence, discern trustworthy information, and negotiate the boundaries of science. Through a grounded theory analysis of subreddit posts and comments, I argue that r/SkincareAddiction users engage in forms of boundary work to preserve the expertise of medical professionals and the perceived infallibility of science. I argue that such delineations both uphold formalized systems of expertise and make space for alternative, community-specific forms of skincare expertise. This community-specific expertise is reified through community norms and agreed upon beliefs, such as the understanding that “your mileage may vary” and “everyone’s skin is different”. I situate these community beliefs within feminist understandings of embodied knowledge and argue that these beliefs are what afford users participation in “expert” conversations from which they might otherwise be excluded.enThesisInformation scienceCommunicationInformation technologyExpertiseRedditSkincareTrust