There are a number of reasons for blushing or flushing of the skin.  Examination by a dosctor is the only way to tell which reason it may be.  It could be normal.  It could be a social anxiety with an unrecognizable trigger.  It could the very beginning of Rosacea.  It could be a thyroid problem.  It could be a symtpom of some disease.  Undoubtedly a doctor could come up with more things it could be.  They are the only ones who can test and really see what is causing it.