If you have tried everything else, and if you think your Seborrheic Dermatitis may be caused by dermatophytes, or especially if someone has athletes feet in your household, Salt and Heat and essential oils may kill the dermatophytes and is a good thing to try. Based on a few pub med articles about salt and heat on Trychophton Dermatophytes, I used a solution of salt water and heat. Then I applied oils of Oregano and Thyme diluted in a carrier oil, and you can add a little DMSO if you have it. The combination of salt water, heat and the essential oils really reduces scaling.
It's only been two days, but I'll update this post in a few days.