I've had this affliction since Nov. 06, which coincided with the start of massive shedding, so it is definately related. It was very, very bad at the beginning to the point of where my entire head was covered in a thick sebum buildup that I would have to scrape away with my fingers. I was hygienic, ate well, exercised daily, was in picture perfect health and it still hit me like a ton of bricks.
My treatment, which has helped bring it dramatically under control:
wash hair with nizoral 2x week / neutragena 2x week / an organic shampoo/conditioner 3x week
*it is possible sodium laurel or laureth sulphate can aggravate this condition
apply apple cider vinegar to your head on a nightly basis
apply either luxiq or olux foam in the morning
take biotin/b complex and fish oil supplements
important: avoid all alcohol/sweets/and anything with yeast in it
also start finasteride if you haven't already...IMO seborrheic dermatitis is a precursor to male pattern baldness
Do all this and I promise you the condition will improve. Dermatologists are quick to prescribe dugs, but while they may be a quick "response" to your situation, they are rarely the whole answer.