I received a heated throw for Christmas and recently my kids spilled some food on it. I assumed that all I could do was wipe it with a damp cloth, but it turns out you can wash them! You do need to be careful when washing and drying and you can not wash as you would a regular blanket.
According to Sunbeam, you need to soak the blanket in cold water and mild soap first before starting the cycle. Do not use bleach or warm water. Once the blanket has absorbed the water start the wash cycle on gentle or delicate. Run the wash cycle for only 2 minutes. Then, rinse in cold water.
You can even start the drying process in a dryer. You need to preheat the dryer on low for 2 minutes then place the blanket in and only run it for about 10 minutes. It will still be damp so you will need to hang dry the blanket for the remainder of the drying time.