I just thought I'd share my experience with pityriasis rosea since reading posts online helped me deal with mine. I had it all over my body, it was incredibly itchy, and I had several 'herald' patches.
First off, I'm going to tell you what worked for me. I'm not claiming a miracle cure, but perhaps some people will find this useful.
1. Cut out sugar from my diet.
2. Consumed probiotics, like Kefir.
3. Stopped taking hot showers.
4. Cut out carb heavy foods (like bread and pasta).
5. Ate a very clean diet, mostly veg and meat (some vegetarians)
6. Got some sunshine on it when I could.
7. Used head and shoulders for 2 or 3 days, but then, on the advice of a doctor from Russia, stopped taking showers altogether.
I can't say all of these actions helped since I was doing them all over the period of having it, but I can say that after 2 and a half weeks my pr is essentially gone (although I've heard that it's a virus that never leaves your body, so when I say the pr is gone I mean the rashes are no longer present on my skin).
I hope this helps somebody, I've heard of people having it for 10 months, I don't know if they were trying these methods, but if you're struggling with it then there's no harm in making these adjustments.
Finally, mine began soon after I came off a course of anti-biotics and just after I finished my final year exams in college. I think stress and a low immune system is obviously connected, but I'd be curious to hear who else was on a course of anti-biotics when it popped up. I would imagine that there is some kind of gut related cause for it, which would explain why doctors seem so confused about how to treat it.
Hope this helps some people.
No reason to despair!