Saddle soap isn't just soap, it is also a conditioner it has waxes and oils that condition and add moisture back into the leather. When the directions are read and followed it doesn't leave a residue, if it did no one would use it on saddles in dusty barns. However, it's made to be used on a wide variety of leather products not just saddles. Follow the directions and always test it first that way there is no risk. cleaning leather isn't rocket science, just takes some common sense.