You can buy new straps for some of the brands. I know this because I stored a carseat in the garage for a couple months and MICE ATE THROUGH THE STRAPS! Ewww...maybe they were squirrels? I can only hope.
The carseat companies say not to wash the straps in the machine, but I have done this a few times. I don't believe that you can "wipe away" vomit. I don't put them in the dryer though.
I would be concerned about weakening the strap fabric if you use too high a concentration of bleach.
_____
Melissa, 34, bronchiectasis (no CF)