Cedar and pine became popular for pet bedding material because they are good at controlling odor and readily absorb urine. They also smell nice because they release volatile compounds such as phenol. Unfortunately these same compounds have been implicated as a potential health risk – possibly causing respiratory problems and changes to the liver. Studies of laboratory animals have shown fairly dramatic changes in liver enzymes on animals housed on cedar bedding. Keep in mind that this applies to all small pets, not just cavies.

If you want to use wood shavings, aspen is a very good choice, as are any of the many synthetic options now available. Another often overlooked alternative is alfalfa pellets (e.g. rabbit food) which are cheap and fairly absorbent.