This is one of the most serious rejection categories. Apps that feature dangerous challenges, unqualified medical advice, self-harm content, or instructions that could lead to physical injury are rejected under 1.4. Here's what needs to change.
What Apple said
“Your app contains content that could endanger users' health or safety. Specifically, the app includes content that could encourage dangerous behavior, provide unsafe medical guidance, or facilitate self-harm. Apps must not include content that could put users at risk of physical harm.”
Apple takes a very cautious position on any content that could translate into real-world physical harm. This covers a wide range: DIY medical procedures, instructions for dangerous activities without appropriate safety guidance, challenges that encourage risk-taking, or content that glorifies or normalizes self-harm. Even user-generated content in these areas can put you in violation.
While you're at it — Apple also requires these pages for every app.
Fix this rejection, then make sure you're covered on the compliance side too. Apple requires every app to link to a hosted Privacy Policy, Terms of Service, Support page, and Data Deletion page. No link means another rejection — just for a different reason.