every couple of years I get an insanely itchy scalp, which seems to always be accompanied by swelling / senstivity to touch on or near my mastoid, both oif which just went away on their own after a week or so. The first time I thought the itchy was a contact reaction following some tree trimming I had done and that soreness behind my ear was a result of my scratching. It recurred without my having done any yard work, and I eventually connected it to having changed shampoos or visited a new hair dresser. However, I have been very careful to avoid use of different products on my head and have not been to hairdresser in very long time and it s baaaack - itchy worse than ever and lasting longer than ever, but behind ear sensitivity is subsiding. Any Clue what may be causing this?