My dolls are stuffed with carded Canadian wool, as its natural, renewable and dust-mite-resistant. You don't have to worry about any off-gassing or toxins from synthetic stuffing.
I also use organic cotton interlock for the body of the doll as in my opinion this is the most ethical choice available. This makes its safer for your child, safer for the farmers and workers, and safer for the earth. Non-organic cottons can be treated with formaldehyde, chemical brighteners, heavy metals, and often still contain pesticides from being sprayed as a crop.
My dolls normally come with custom dyed and spun wool yarn for the hair, which only adds to the dolls character.