Some are born with a form of eczema, called Atopic. Like you I didn't get eczema until later in life at age 50. I now have multiple forms,GD being just one of them. Those with eczema are prone to getting multiple forms. You mentioned Seborrhea Dermatitis. Have you been tested for Allergic Contact Dermatitis, ACD which can cause itching all over the body and may or may not show a physical rash. That happened to me but the 5 Day Extended Patch Test identified my allergens so now know what to avoid
Do go see multiple dermatologists, I have been to over 7 in the 20 years since I started up with eczema and do learn from each. Also consider an allergist as they also can administer the 5 Day Extended Patch Test, the True Test Kit is popular and yes this test takes 5 days it is not the 30 minute environmental prick test. Google it.
Right now in remission with all 3 forms of eczema. Yet I always have a few papuales and scabs on my lower back torso even in remission, but not an issue. Our cellular structure has changed with GD.
Study so you know to ask the right questions to ask doctors. Always get second opinions but do not share what previous doctors tell you. I had a good derm who was treating me correctly for 2 forms of eczema and incorrectly assumed one new type I got was simply one of my previous forms.. Treatment all wrong. These derms treat hundreds of skin diseases and are more knowledgeable about certain type. I went to a new derm who took one look and identified it correctly.
Go to dermnetnz.org, their skin site is the most complete I have ever found, better than the NEA by far. Great photos.
I am definitely better with all eczema since I now follow (as mentioned dozens of times) the William Crook, MD The Yeast Connection Handbook diet. Please suffer though the detox period and then follow the maintenance plan, you will know within 3 months if diet makes a difference. So much easier to pop a pill or put on a topical- this diet is brutal! Yet for me the rewards have been great. I am leading a normal, controlled yes, but productive and happy life again.