The over use of antibiotics is a leading cause of yeast overgrowth.  A stomach void of natural acid has lost its major defense against the bacteria that are, unavoidably, in our food, etc.  Disturb the external ear with a q-tip and you may get an external ear infection.  Douching...

Douching, more than other feminine hygiene behaviors, can be a significant cause of bacterial vaginosis (BV is a bacterial infection in that part of the female body); that is, it is not simply a response to the bacteria; it may be a cause of the bacteria.  In other words, the body can usually take care of itself; we have to live with germs and removing all of them has to be unhealthy.

"After adjusting for demographic and sexual behavior factors, neither type of underwear (nylon vs. cotton prevalence ratio (PR) 1.05, 95% CI: 0.97–1.13), menstrual protection (tampons vs. pads; PR: 1.04, 95% CI: 0.95–1.12; pads and tampons vs. pads 1.00, 95% CI: 0.92–1.07), use of pads or panty liners when not menstruating (PR: 0.99, 95% CI: 0.95–1.05), nor weekly or greater use of hygiene spray (PR: 1.01, 95% CI: 0.94–1.09), powder (PR: 1.02, 95% CI: 0.96–1.07) or towlettes (PR: 1.03, 95% CI: 0.94–1.13) were strongly associated with BV. PR for daily versus less than daily bathing and showering were 1.06 (95% CI: 1.02–1.12) and 1.04 (95% CI: 1.00–1.09). Douching remained associated with BV (PR for weekly or greater vs. never 1.17, 95% CI: 1.09–1.26) and was not substantially impacted by adjustment for other hygienic behavior."

Klebanoff MA, Nanse TR, Brotman RM, et al. "Personal Hygienic Behaviors and Bacterial Vaginosis." Sexually Transmitted Diseases:  February 2010 - Volume 37 - Issue 2 - pp 94-99