A few days ago, I emailed Divacup to ask why hydrogen peroxide isn't recommended for use on the cup. This was their reply:
Hydrogen peroxide is just not good for the silicone. We have been told by
the manufacturer of silicone parts. Rubbing alcohol has been tested on the
DivaCup, and we are sure that this is safe to use. Also, hydrogen peroxide
can leave residue and that wouldn't be great for the vaginal environment.
Have a great day,
Diva International Inc.