To turn your nose up at something

To refuse to take or accept something because it is not good enough for you

e.g. I love to buy clothes in charity shops because I get real bargains but my best friend is embarrassed even to be seen in those shops; she turns her nose up at anything that doesn’t have a designer label.

The idiom comes from the tendency to raise your chin (and so “turn your nose up”) at something you don’t like/approve of.