Abstract
Social media influencers serve as a key source of health information for adolescents but often lack expertise, have commercial motives, and may spread misleading or harmful content. This study examines the health-related content shared by influencers, the prevalence of advertising, and how adolescents evaluate potential benefits and risks. Using a mixed-methods approach, we employed a quantitative descriptive method involving citizen science (Study 1) and a qualitative content analysis (Study 2). In Study 1, 336 adolescents from 16 Austrian schools documented and categorized 2,147 posts from 255 influencers. The most common topics included sports and fitness (50.5%), beauty ideals (29.6%), food and nutrition (27.6%), and cooking (19.1%). Although advertisements appeared in 41.5% of posts, adolescents rated 60.4% of them as beneficial and only 4.5% as harmful. The qualitative analysis of a subsample of the 90 most prominent posts showed that adolescents appreciated motivational aspects (e.g., healthy eating) but often overlooked problematic elements such as misleading claims, sexualized body ideals, and the linking of health messages to commercial products. Enhancing persuasion knowledge and critical thinking through education, along with stricter regulation of harmful products, is crucial to safeguarding youth online.