There are no chemicals in reusable nappies!
Within disposable nappies there are various chemicals present to help absorb fluids, to keep the wetness away from the bum and perfumes to help contain the smell. One such chemical sodium polyacrylate use have been discontinued in tampons because of its ties to the toxic shock syndrome. No long term studies have been done at this stage but 24 hours exposure to these chemicals can be seen as a threat to your babies health.
There are no chemicals in reusable nappies so there is no exposure to these chemicals. There cannot be any allergic reaction to the chemicals nor can any damage be caused by the chemicals. This is healthier for your baby.