If you go through labour before your C-section, your perineum may still become swollen and sensitive. Passing gas or doing a number two can be difficult and straining will likely aggravate your incision and sore abdomen.
If your C-section was planned, the location of your incision makes bending over your vagina and bottom difficult. An upside-down Peri bottle helps you clean up without bending too far to reach down there. Plus, you can use it to clean your incision to avoid infecting the wound.