During the first week of CG it's OK to CO wash even everyday (though not ideal...) and the itching is a sign of healing, however, if there is itching after several weeks the cause could be different. If it's due to dryness, washing of any kind, unless it's done with a rich CO, is only going to keep compounding the problem by removing any trace of sebum from the scalp.
My suggestion would be for you to get a good oil such as jojoba or virgin coconut oil (easily found at Indian grocery stores) and do an overnight treatment. All you do (at bedtime) is massage a little bit of oil at a time on your scalp with your fingertips until you've massaged all of it, then you rub a few drops of oil in your hands and smooth it mainly over the top of your hair, any dry parts and the ends, then wrap your head in a scarf or sleep bonnet. When you get up remove the oil in the shower by washing with CO, then proceed as usual. You could also add a few drops of the oil to your current CO.
2A/3A, medium length, layered, colored dark/medium ash blonde - "CGer" since April '02.
"Converting the 'curlskeptics' one curly head at a time..." HWHC