I only hand applique and I don't usually prewash, but lately I find that the skin on my fingers and cuticles start drying and peeling. Between projects they are fine, but when I start another project it comes back. I will prewash the next project and see if it makes a difference. I don't know if it is the chemicals in the fabric, or handling the fabric more than in piecing, but if you have sensitive skin, it would be a good idea to prewash.