How much cardboard is too much?

Question
I know cardboard and paper is acceptable for bunnies to chew on and occasionally they will eat some of it. But how much ingesting is too much?  I have 2 rabbits, a boy and a girl both recently spayed/neutered and are just over 4 months old. They love to chew on cardboard but I'm nervous about them ingesting too much. Am I being overly cautious?  Also I've caught my girl chewing on the edge of the carpet as well. It makes me nervous about impaction. Any advice?

Answer
Dear Donna,

I think a bunny would have to ingest a LOT of cardboard to have a problem.  It's made of cellulose, after all.  As long as the cardboard isn't bonded with any plasticizing agents or glue, I would not worry. I've never heard of a rabbit having a problem from ingesting bits of cardboard.  How much do yours actually swallow?

I would, however, keep them away from the carpet.  Anything synthetic will not be digested, and can potentially cause a blockage.  

Provide plenty of hay and fresh, wet greens to help push things through.  And maybe put hay inside the cardboard box to encourage them to eat that, instead of the box.

Dana