Responding to the question, Dr. Rajab Abu Maleeh, PH.D. holder and shari`ah consultant at islamonline.net, states:
We had got to clarify specific impure substance used. So, if it is alcohol, it is permissible to use such perfumes and cleaners that contain it. Though being prohibited to consume, alcohol is not najis in itself.
If you mean other impure substances, such as pig fat and the like, then the ruling is ‘unless these ingredients are put to chemical operations that change them into pure materials, it is unallowable to use them because they are filth and najis.’