One of the conditions that came along with my fibromylagia was this 
sudden seborrheic dermatitis on my scalp. It was incredibly itchy and 
scaly on my scalp. The itchiness drove me NUTS!! I finally have stumbled
 upon an all natural solution (my doctor just wanted to give me a 
prescription.) 
Dead sea salt! I 
bought a container in the beauty section of Whole Foods, and made sure 
it was JUST the dead sea salt, no fragrances or ANY other ingredients 
besides the salt. ($15) For the first few nights I'd get in the shower 
and run warm water over my scalp, mix some of of the sea salt to 
dissolve in a cup of warm water (about 8oz size) and then I'd pour the 
warm sea salt mixture over the back of my scalp (where the dermatitis 
was the worse). I have long hair, so I rubbed in the salt mixture and 
piled on my hair. Then I either stepped out of the shower and wrapped a 
towel around my head for about 10 minutes, or I'd busy myself wit 
something like shaving my legs :) The main points to take away are the 
initial warm water opens up the pores in your scalp, then allow the sea 
salt to set on your scalp for a few minutes to soak in (5-10 min). Then 
rinse off. I did this for 3-4 nights initially, and then the remainder 
of the week I switched to the sea salt mixture (water and the sea salt) 
in a spray bottle - when I came home from work I'd spray the sea salt 
water mixture on my scalp, rub it in, wrap with a towel for @ 10 
minutes, then step in shower and rinse. I was amazed, after the 1st two 
days I def noticed less itching and a difference! And, after the first 
week of treatments, no more itching! So now 1-2 times a week I'll use 
the spray bottle of salt water treatment just to maintain the clarity of
 the dermatitis.
Of course if you live near the ocean, just go hang out in the ocean on the weekends! Even more fun!
Also
 good to note, I had bought some lavender oil to help sooth the 
itchiness, this did help soothe that - temporarily. While it did not 
treat/cure the dermatitis, it did help get me through until the sea salt
 kicked in! (It took me a while to find out the sea salt cure, so the 
lavender oil was def helpful.) 
I hope this helps!