Re: Pump is causing blisters
Just a shot in the dark - maybe the flange size needs to change? I've heard from some moms that breast size/shape can change over the course of breastfeeding, and a flange that fits in the beginning may not fit as well later on and they have to switch to a different size. If that's happened for you, and the flanges aren't fitting properly, they could be rubbing/causing irritation. Do you have other sizes to experiment with?
Re: Pump is causing blisters
Good suggestion from the PP.
When I hear that a mom who has been nursing/pumping for a long time with no problems is suddenly having pain or skin changes (including things like blistering, cracking, dry or flaking skin, nipples appearing red/pink/shiny), my first thought is thrush.