They can be washed, gently. Don't do it too frequently; you should get several wearings at least between washes.

Use cool water and Woolite or mild shampoo (I'd go with the Woolite, it's made for washing nylon, which is what most fake hair is). Press the excess water out in a towel, don't scrub the hair with the towel. You don't want to agitate the item or do anything that will make it matt up. Gently comb out the snarls, using your fingers as much as possible, and/or a wide tooth comb. Air dry it. Most synth hair won't take heat.

Wonderful!

Thank you!

Azeeza