You're very welcome. I can strongly relate with everything you said in regards to blood tests, diet, and healthcare.
Before skincare, I have to mention that certain food eliminations help with the triggers of my SD and oily skin. Despite my "normal blood test" results, refined carbs and dairy can worsen these issues for me if I eat them in excess. I just consume them in moderation.
For my Seborrheic Dermatitis , I consistently stick with a dandruff shampoo (Head & Shoulders) during every wash and it has made a significant improvement. I noticed results after the first two weeks of usage. Along with using an ointment called Sulfur 8 on the scalp afterwards to prevent flaking. The shampoo is very drying but it's the only one that alleviates my dandruff unlike others. Moisturizing hair products help with this but I'm going to find a more mild alternative.
For oily skin and acne, this is kind of complex for me because my menstrual cycle can influence the triggers regardless of the type of skin products I use. My skin surprisingly becomes better afterwards.
But the products are:
•Ole Henriksen Counter Balance Oil Control Hydrator Moisturizer (it's very expensive but it's the only moisturizer that has reduced my oiliness and maintained a matte finish)
•Mineral Zinc Oxide/Titanium Dioxide sunscreen for overall sun protection.
This surprisingly helps with my Acne flare ups because of those two main ingredients. Chemicals subscreens with Avobenzone and Oxybenzone always break me out.
These products and dietary modifications aren't cures but they have personally alleviated my acne, oily skin, and dandruff from coming back.
I'm still trying to work with my endocrinologist because the skin issues are still indicating an underlying problem that could benefit from some medication but they have to properly investigate it first.
Also, I hope you don't find this offensive but the only skin kind of makes us look extremely youthful and supple despite the constant blotting. It's like a blessing/curse for me.