I think the Fels Naphtha soap is, by itself, meant to be a laundry soap. It's been around forever. It's been used for years for laundry and even to help prevent poison oak outbreaks. I think you may use any bar soap, but Ivory is the brand I've seen most used. I've also heard Zote as another popular choice, but have never found it locally. I know one can buy in online.