I used carefresh back when I had rodents; they liked it because they could shred it to build a nest. I found that it didn't do much for the oder but made it easier to spot clean. It is a bit dusty and the rats would sneeze a bit the day I did the cleaning, so I don't know what it would do to a snake's breathing.

I will say though that as someone in your roommate's shoes that I've found that while I'm allergic to coconuts, cocohusk is actually one of the few that don't give me hives. Every moss I tried did, aspen does, and some of the dustier substrates make it impossible to breath, but cocohusk has yet to make me react.