My story in a nutshell: I'm 38 years old, male, and have been pretty constantly affected by seb derm for the last 20 years. In the early days I would use steroid creams to clear it up, then in the last 10 years resorted to anitfungals, which took longer to get the flare-ups under control (and never completely). I was blighted in the usual places: crooks of the nose, eyebrows, chin. It's a miserable condition but I'm happy to say that I've been completely free of it for the last six months.
Obviously, each of us is very different, our genetic make-up very unique, and what works for some will not work for others. But to cut a long story short, earlier this year I made a concerted effort to rid myself of seb derm. Firstly, I cut out alcohol and started eating a ketogenic diet, and a strict one: practically meat only, zero carb. I also started to moisturize with 100% caprylic acid. I can't say if this had any effect at all (we'll get to that in a minute), but after reading an article somewhere, I decided to also throw out all the products in my house that contained SLS (sodium Laureth/Lauryl Sulphate). I'd read that it was a very potent skin irritant and yet virtually every beauty/washing product you can lay your hands on has it in abundance.
The results: my flare-ups lessened by quite a degree but I could still see the slightly reddened areas in all the usual places. I wasn't using any SLS in the shower. Was there anything I was missing? Yes: toothpaste. Sure enough, SLS in the toothpaste. Hiding in plain sight. So I switched up with a natural, non-SLS toothpaste and ever since I have been completely free of seb-derm. To be sure it was the SLS, I restarted eating carbs and drinking alcohol and neither action has proved detrimental to my skin. I haven't stopped using the caprylic acid to moisturize but I have gone days travelling without using it and no ill-effect so I'm fairly certain the biggest culprit for me was SLS.
So now I wash with a sea kelp soap (nova scotia is the brand I think), SLS-free shampoo and JASON toothpaste. While I eat low-carb generally, I don't believe that my diet has any effect on my experience of seb derm.
So there it is. Try it out: eliminate SLS (don't forget your toothpaste), moisturize with 100% caprylic acid, and see if it helps. It turned my skin around in a matter of days.