I use an electric blanket that is older than I am. My parents got it when they first got married. I have washed it several times -- gentle cycle, no bleach. I've even put it in the dryer.
Of course, they don't make 'em like they used to! So you never know.
I have no idea what the brand is -- that part probably faded off a decade ago.
I love mine, and it hasn't fried me yet. I tell people that if it ever does, to know that I died warm and happy.
I had an electric blanket years ago, left it at my Mom's when I moved to Colorado. (What was I thinking???) I remember washing it and never having a problem. There was care information in the package if I remember correctly. I think they are a great, keep you toasty ad you don't have to heat the entire house.