The card does not speak of the back, the chest and rashes. It calls the tar soap a product for problem skin of the face and body; the short description says that it reduces redness and soothes irritation – the card gives no confirmation of this. The composition has tar (birch oil), kaolin, glycerin and olive oil.
General information (not a manufacturer's instruction): in case of rashes, inflammation and skin changes of unclear origin, it is better to see a doctor.