Somethings are antibiotics, stress, steroids, hormones, birth control, and eating a high carb/sugar diet.
One course of antibiotics can disrupt your gut bacteria for at least 6 months!! (More to come on that soon.)
Candida only becomes bad when overgrown and can easily do so in dysbiosis.
"Candida is a masquerader, it's hard to find, hard to identify, hard to diagnose and hard to treat." - Holt IFNCP
Your diet (what you consume) plays a massive role with Candida. It feeds off all the processed, carby, sugary foods. A lot of what we consume these days. It THRIVES in this environment. You have to stare the little buggers to help kill them off. But the cravings the overgrowth causes are hard to beat alone.