I'm 26 and have been suffering from seborrhoeic dermatitis for as long as I remember basically. Over the years I've developed a routine for my face which I'm pretty happy with as my face got a lot better and the red patches basically never appear on it anymore but for the past two or so years I've been battling a new problem - red, itchy and scaly patches appearing on my chest and back and strong acne on my back. Here are the photos: https://imgur.com/a/x8oJqJT
Sometimes the patches just come and go, sometimes they appear and stay there for weeks easily. Often they're itchy though sometimes they're not. The only thing I found that sometimes works on these is the cream I use for my face at night, the La Roche Kerium DS Creme. Even that doesn't bring sensational results though, it just calms them up a tiny bit if used meticulously for a few days.
As for acne on my back (which is really weird cause I don't have any on my face), I've tried using salicylic acid solutions for it along with manuka leaves cream as I've heard people had success with that but the results of those weren't great to be honest either.
What else could I try? I've talked to my dermatologist about it but he said it looked like pityriasis rosea and should resolve on its own. He gave me some ointment for that but that was a long time ago and since then it never really disappeared for good so I'm not sure if that's really it. Any other home (as in, OTC) remedies I can try, now that the access to doctors is still hard because of covid?