It sounds like mild eczema. I can't even think of what else it could be. By all means see a dermatologist, but I wouldn't worry--this does not sound serious or allergic. As for why it comes and goes, that's just what eczema does. A little weak (1/2%) hydrocortisone may help speed the recovery, though it usually comes back, at least for a while, in which case you either treat it again or just let it ride if it's mild.
Best.
Dr. Rockoff
Dr. Rockoff