Your Magic Sleepsuit and Dream Sack can be machine washed cold with like colors and tumble dried on the low heat setting. Hanging to dry, especially for the cotton version, will help to prevent shrinkage (inside out is the fastest hang-drying method). As with all cotton goods, there may be a small amount of shrinkage due to laundering. 

Avoid hot water temperatures and high heat drying, and use only non-chlorine bleach if necessary.