Head and Shoulders never did much for me. In fact, I would itch even more when I used it. I think it might have just been too harsh for me.
Selson Blue was my favorite "dandruff shampoo", but I am finding for my particular scalp conditions, that I am doing better with a tea tree oil shampoo and a gentle shampoo. I like the GVP Tea Tree Oil Shampoo from Sally's and I alternate with the One n Only Argan Oil Shampoo. Occasionally I will throw a few others into the rotation, but the tea tree oil seemed to make the most difference. I don't know if shampooing 1 time per week is enough if you are treating dandruff. I would think every other day or every three days until you got it under control.