Going topless, or wearing a bra that is sized right are both ways to minimize the itch. I find that the itch just happens sometimes, even when topless. I have recently discovered that the Vaseline brand Intensive Rescue Clinical Therapy cream applied in very small amounts and worked into the nipple well gives great relief from the itch for about 12 hours. The one I bought is unfragranced. After 3 days of washing the nipples and re-applying it each morning and night, the itch is pretty much gone.
It was driving me nuts. I hope you find this helpful.