“A friend who knows what they’re talking about”: Extending source credibility theory to analyze the wellness influencer industry on Instagram

While many scholars have explored the norms central to the success of social media influencers, credibility is a necessary attribute of creator presentation that remains underexplored. This essay argues for the application and extension of source credibility theory (SCT) to unpack how credibility manifests within the wellness influencer industry on Instagram. SCT originally included three constructs: expertise, trustworthiness, and attractiveness. I extend this theoretical framework by considering a fourth construct: positionality. When applied with the additional construct, SCT can help explain how influencers build and maintain credibility over time, especially within the wellness industry, where some influencers do not have more traditional forms of expertise like degrees and certifications in a health-related field. Through in-depth interviews with wellness influencers across the United States, I detail how credibility is operationalized within the wellness industry on Instagram and utilized to build relationships with followers and grow successful businesses.