Why don't you use a preamp before the comparator. It will solve maximum of your problems. Well it depends on the exact application but usually preamplifiers come handy in these problems.

Hi,

I also agree with the pre-amp idea. Nevertheless, here are a couple of additional thoughts:

1) Quantify the incoming noise: assuming it is gaussian noise, either flicker or white noise, the pk-pk noise will be given by 6σ. Therefore you could quantify the hysteresis of your comparator based on this number as a minimum required.
2) In case the incoming noise is larger than what you can afford for the comparator hysteresis and for any reason you cannot use a preamp, if it is flicker noise you could chop the amplifier (and you should clock your comparator too) so that you remove the flicker component from your signal band (in addition you would be removing the comparator offset component too).
3) You could add an analog delay at the comparator output: for example integrating a current into a cap will allow filtering some of the noise driven toggling your comparator might experience. This delay might or might not be an option depending on your application
.

Hope this also helps
Tosei