How come some pathogenic micoorganisms are commensals in our body?

[scilearner]

For example candida fungus is a commensal in our skin and mucus membrane, but it can cause infection. So I'm asking why is it not causing infection in everyone, are the commensal form of candida harmless, so to get the infection we must inhale patogenic candida. Thanks

[sammy7]

hay i dont know a ton about it but a lot of practioners who deal with kids with autism do, ie candida albicans is normally present in the intestines i think but in certain circumstances (screwed up intestinal transit time lack of bile etc etc) it gets out of control and starts dominating (where as normally the "good" bacteria i think all the lacto's and bifido"s and the other zillions man probably doesnt know a thing about) usually keep it in "check" i think so to speak, so yeah it gets out of control and causes some nasty symptoms (these practioners would say) just google "candida albicans autism" and youll find tons of articles on candida and some unpleasant effect some people claims it causes.. ( i dont think the mainstream medical model even believes it exists so...).hope that helps.

[CharonY]

This is because not all organism are pathogenic all the time. With a functioning immune system and a healthy flora many of these are harmless. Only once something happens to upset this (e.g. some other infections, weakening of the immune system etc.) do they start to become harmful.