Why do I breakout when I try new products on my face??is it because my skin is adjusting to it??

My sister used to have a lot of breakouts and she always says that nearly everything she reads (apart from by dermatologists) is rubbish. She says things you see in adverts are rubbish, things people say about their own skin (i.e. that breaking out is good for your skin, that X, Y or Z has caused the problem, that you should do a specific thing and that there's an easy cure) is all rubbish. It can be really difficult to know the real cause of a breakout and often it's something you couldn't have controlled anyway.

The advice she always gives people is to see a dermatologist (and to listen to their advice).