In the early 1900s, Curie discovered that Radium destroyed diseased human cells faster than destroyed healthy cells. A whole world of commercial uses for Radium was unleashed. Dr. C. G. Davis wrote in the American Journal of Clinical Medicine that "Radioactivity prevents insanity, rouses noble emotions, retards old age, and creates a splendid, youthful, joyous life," Everything from, toys to chocolate, soap, eye drops, and condoms were imbued with Radium for their supposed health benefits.
The reality was that radium was 2.7 million times more radioactive than uranium and this wasn't realized until the 1930s and 40s.
In hindsight, this is unfathomable, almost laughably so. A natural question to consider is — what blindspots do we have now in our current beliefs? This question isn't limited to medical beliefs, but can be extended to any of our social norms.
As has become even more evident during the Coronavirus Pandemic, it is difficult to come to scientific consensus on the first pass. Guidance from authoritative public health organizations on the effectiveness of wearing masks in public shifted dramatically over the course of one month. Ideally, our views would have been more accurate from the beginning, but changing them was necessary once new facts emerged.
It's important to remember that history isn't solely a story of the past, but also the present. Just as beliefs have evolved drastically in the past, so they will continue to evolve. Don't be afraid to change your mind or be convinced that you're wrong. It's not a sign of weakness to question your own beliefs from time to time.