Of course they can be washed, but only the outer sleeve. All our designs have two covers, one inside and one outside, so you can wash without any problem the outer cover of the heat pillow for microwave without fear of wetting the seeds and flowers in its inner cover. By simply removing the outer cover you will always have it clean and ready to use.
As it is 100% cotton fabric, washing is not a mystery, since it is a fiber that is easy to treat and very resistant to washing, both by hand and machine. You can choose between hot or cold water when you go to wash the cover, but if the temperature you use is very high (over 60°C) may lose color and shrink a little, it is recommended temperatures no higher than 40°C.