I have been having trouble with dry scalp and dandruff, because I haven't been using Selsun Blue. I haven't been using any type of shampoo; I've only been using my Castile soap mixture. A while back, I bought 100% pure Tea Tree Oil from Whole Foods. It costs about $11.00 for the 2Fl Oz bottle above.
I had been using the Hollywood brand, but I think the real oil is better. I researched the benefits of it, on a few websites including KinkyCoilyCurlyMe & Daily Glow.
Today, I did a pre-poo with Castor Oil on my hair and the Tea Tree Oil on my scalp. I also put about 10 drops in my Castile soap mixture to cleanse my hair. It was recommended that you use the Tea Tree Oil on your scalp daily. However, the fragrance is very strong. I might try to apply it to my scalp at night. I will give you all an update soon!