Here is Olfa's response to cleaning mats. I have used it often. And remember about distortion through heat!!!!
"Fleece fibers are naturally attracted to your self-healing rotary mat. To clean your OLFA mat, use a generous amount of room temperature water and a few drops of mild detergent. Use a soft, mild bristle brush such as a toothbrush or mushroom brush to create a lather and gently clean your mat. Rinse with room temperature water and wipe dry with a cotton towel. Please note that warm or hot water and direct sunlight may damage the mat.