I had seborrheic dermatitis on my scalp, face and back. I think it is in the same family. I no longer have this problem. What helped was:
More frequent washing (2x per week) with a regular shampoo and conditioner (ORS Uplifting Shampoo is my favorite). I dislike presciption shampoos b/c they dry out my hair.
Taking a multivitamin w/ biotin. Mine is a supermultivitamin and has biotin included. (Most important IMO)
Using scalpacin, an over-the-counter topical alternative to prescription medication. I used this for a while also. (May cause irritation until the wounds/rashes heal) Once dry, apply a little hydrocortisone cream in affected areas.
Try not to use grease on the scalp. It will have adverse effects.
Hope This Helps . . .