I was attracted to trying out superwash wool because it is a natural fiber, and because it can be washed in the washing machine (A big deal when knitting for children, especially a little boy.) without felting. Little did I know at the time, my assumption of it being a natural fiber were false.
In order to make so that the wool doesn’t felt, the scales that make it stick together have to be removed. This is done by harsh chemicals. Some superwash is then also coated by a thin layer of polymer (plastic), which makes it more toxic than those just treated with a chemical bath.
Superwash wool is labeled as 100% wool even if it has the polymer coating (This is the main reason for my faulty assumption it was a natural fiber.). The only way to know if it has the polymer or not is to contact the company.
I’ve chosen to not use superwash in the future. I’m looking into other wool, and washing options for my future projects.