As a copywriter in an agency setting, sometimes you get to write a lot about things that interest you – food, travel, sports, social issues. And sometimes you have to write about dry mouth. Thankfully, I've become an expert in quickly becoming an expert in things I previously knew next to nothing about. My work with Aspen Dental is one of many examples of that.
I still wouldn't trust me to do any pro bono root canals or anything though, so don't get any ideas.