Is self-touching always a flirting signal?

I'm often in a reading room (or is study hall the appropriate term? English isn't my first language, so any correction would be nice :) ) in college.

I often sit near the doors, so girls have to walk past by me.

Many touch their face (cheeks, lips, ears etc etc) as they are passing me by.

I've googled it - but I want to ask you girls here, is it always 100% flirting?
Is self-touching always a flirting signal?
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