Many things that were once "common knowledge" are now known to be false. That's why modern evidence-based medicine is increasingly effective and offers the only viable path forward. But it also makes me wonder what things we currently consider to be common knowledge today will be as thoroughly debunked as bloodletting 100 years from now.
Bloodletting has been an important and scientifically verified part of my father and aunt's medical treatment due to an excess absorption of iron (haemochromotosis).
Also some people find leaches useful for cleaning wounds.
Common knowledge is like a common cold. You just don't want it.
