Dry, itchy, scaly spot on left eyelid only

I have a dry, itchy, scaly spot on my left eyelid only.  No problem on the right eyelid.  I went to a dermatologist about a year ago and he prescribed an ointment that seems to help for a couple of days and then, the spot comes right back.  It can't be an allergy because it only happens on the left eyelid.  It is so aggravating and irritating and I'm going crazy trying to figure out what it is and what is causing it.  The dermatologist said it was blephoritis.  I'm not so sure.  I just really don't know.  Does anyone know what I can put on it to get rid of the itchy spot once and for all?  Please help.  Any suggestions will be greatly appreciated.

[Lbliny]

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