Medications include antacids, which neutralise acidity of gastric secretions, and proton pump inhibitors, as well as H2 receptor blockers, which decrease hydrochloric acid production in the first place.
They synthesise vitamins in your gut, neutralise acid in your mouth, help balance your immune system, and they take up space preventing harmful bacteria from getting in.
During the same period, the discovery of antibodies and their role in neutralising pathogens also came to light thanks to German physiologists Emil Behring and Paul Ehrlich.
Each of the versions of this protein that exist in every individual is capable of locking onto and neutralising a different invading pathogen, by interacting with different molecules on the pathogen's surface.
If their teeth aren't brushed, then, goodness me, the plaque that will build up, the acid in their mouth that won't be neutralised, their enamel will be worn away.