I have often been bothered by itchy skin. The two main causes with me are skin problems caused by a autoimmune gluten sensitivity called Celiac Disease. See http://www.celiac.com.
I also itch when ever I get certain chemicals on my skin. Because of this I use only borax for washing my body, hair , clothes and bedding. I'm sensitive to many commercial body products so don't use them. There are some vitamin and supplement combinations for healthy skin.
It may help if you can't find a cause to use one of the cleansing programs on the Liver Flush Support Forum .