The Spread of Non-Evidence-Based Health Claims on Social Media: The Case of #Mouthtape on Instagram, a Cross-Sectional Study.

Background: Social media platforms like Instagram have become major sources of health information, often amplifying unverified claims. Nocturnal mouth-taping is one such trend promoted as beneficial for sleep and overall health despite limited scientific evidence. Methods: In April 2025, 530 Instagram reels tagged #mouthtape were retrieved via the official API. After exclusions, 390 reels were analyzed. Two independent reviewers assessed each reel for relevance, stance on mouth-taping, presenter characteristics, engagement metrics, and content type. Spearman's correlation, Mann-Whitney, Kruskal-Wallis, and Chi-Square tests were applied. Results: Overall, 94.4% of reels endorsed mouth-taping. Most content was produced by companies (55.4%), while only 11.6% was posted by medical professionals. Supportive posts had significantly higher shares than critical ones (mean 923 vs. 193; p = 0.015). Male presenters' reels achieved more likes and shares, though female presenters had more followers. English-language posts generated greater engagement. Commercial and medical claims predominated, with limited representation of evidence-based information. Conclusions: Instagram content overwhelmingly promotes mouth-taping, largely driven by commercial actors. High engagement with supportive posts, regardless of scientific validity, underscores the role of algorithms in spreading non-evidence-based health claims.