I have used all sorts of shampoos and home remedies. What has finally helped was:
1) shampooing twice a week, no ifs, ands, or buts
2) Using a pre-shampoo treatment. I vary these.
The 'milk' treatment, discussed in another thread has been very helpful.
Also, I've been using the cayenne pepper and vodka treatment. That really took care of it for a while.
(Be careful not to scratch before using this one. It stings!)