Any time I get the itchy dry scalp problem, I fall back on my favorite homemade cure. I have dry skin, and I knew I needed to moisturize my scalp, but we all know hair and grease don't go together. First I tried plain old veggie oil in my hair, but it was an ordeal to remove.
So try this one night, and the following night if necessary. It works great as long as you are just experiencing dry scalp or seborrehic patches (cradle cap stuff).
In a little bowl mix about 2 T oil (any type in your pantry) and 2 T hair conditioner. Mix them well. Hair can be either dry or just washed. Place a towel over your shoulders. Sit in front of the TV and find a good show. With your fingers, part your hair and dab on the mixture onto the scalp. After your entire scalp is covered, sit and watch the show and massage your scalp, concentrating in any bad areas. Go to bed with a towel on your pillow.
In the morning, wash your hair as normal, or twice. The conditioner in the mixture allows the oil to wash out without shampooing 5 times.
Seriously, try it, and post how your scalp feels the next day. I tend to do this semi regularly during the winter months. Most dandruff shampoos dry my scalp out even more, and this seems to work wonders for me.