First off, I REALLY wish people wouldn't confuse dandruff with dry scalp. They are two totally different things and treating dry scalp with a dandruff shampoo like Head & Shoulders/Selsum Blue/T-Gel can make things ten times worse, further drying your scalp out.
I'm so happy H&S has a shampoo specifically for dry scalp now. We moved from AZ to Germany and the humidity has been crazy so we've been running a dehumidifier 24/7, which I think is why my scalp is dry. I've tried Regis Line Olive Oil shampoo & cond., Nexxus Humectress and L'Oreal Everpure Moisture Shampoo. Even when using those, as soon as my hair air dried I'd part my hair and see the big white flakes. And then the itchiness would set in. I figured since my scalp was dry it would need a moisturizing shampoo. I found this on a whim and gave it a try. First time, no more itchiness and flakes are much smaller and fewer. Second time using it... No more flakes, itchiness, nothing. Just clean, shiny, soft hair. I am SO impressed, love it!