Don't wash it; it's like troll hair. It's not rooted, it's just a mat of fake furry material glued into a runner down his head and a little plug on his tail.... water isn't necessarily going to make it come out immediately, but it will soak into the glue and the root material.... he will probably get mildewy and smell TERRIBLE. If there's gunk on his hair, try wiping it with a damp paper towel, but do NOT soak it.