Each summer, a familiar falsehood returns to digital circulation: that sunscreen, the very tool designed to shield us from skin cancer, is itself a cause of it. The scientific consensus is unambiguous and long-established — sunscreen is safe, effective, and protective. Yet the myth persists not because the evidence is unclear, but because fear travels faster than fact, and the architecture of online sharing rewards alarm over accuracy. This recurring cycle asks a deeper question about modern public health: how do we make truth as contagious as the lies that undermine it?