I have been using Optimum Oil Therapy for some time now and have been having this itch for a long time; over a year. If I get a perm, I will be straight for a few days and then the itch is back, same happens when I wash and condition my hair. Also, it's always the crown and and around my hairline.
Ok, yeah yours sounds like mine.
I've tried everything. Definitely start taking lots of flaxseed oil. And continue to focus on rinsing your scalp well. My theory is that your scalp in those areas is drier there than the other parts of your scalp. This may sound weird, but what I have found helpful is to apply a very light oil to the damp scalp after washing but before styling, just to where my scalp gets itchy to seal in moisture. I liken it to applying lotion to damp skin in the winter time to prevent the itchies. I rollerset, and I always notice my scalp acts the fool later when I don't do this. Right now I am using Parnevu scalp oil b/c it has a nozzle tip. When it runs out, I'm just gonna refill it with some of my other oil (probably jojoba next). I don't apply any more to the scalp after that. Also, I do a first lather with Elasta QP scalp stimulating shampoo b/c it has salicylic acid (pyrithinone [sp?] zinc, sulfur, etc made it worse for me) and has sodium myreth sulfate (very mild). And I like that it's purple and tingly
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You may want to check out Lisa Akbari's books. She focuses a lot on scalp care and all the different issues we can face.
Good luck with the scalp and HTH