From the cRc:
“Bar-soap has always been made from (non-kosher) animal fat and there are respected halachic authorities that hold that one should not use such soap for washing their body. However, the common practice is to be lenient on this issue because (a) many disagree with the aforementioned opinion and (b) some argue that our soaps are sufficiently inedible that even the stricter opinion would agree that they can be used in spite of their being made from non-kosher animal fat.”