Online health information systems evaluate content by its alignment with medical consensus, treating that alignment as a reliable signal of safety. In peer-to-peer health discourse, that assumption fails: advice that is factually accurate is not necessarily safe to act on. This paper identifies and empirically validates the Online Health Safety Gap, a structural misspecification in which medically accurate content can carry substantial health risk. Across 704 health narratives (699 classified), two scores computed from non-overlapping feature sets, Narrative Truth Distance for epistemic divergence and Narrative Risk Score for health risk potential, share only 4.9% of their variance (r=0.222, p