There has been a lot of controversy regarding the use of pine shavings as litter for rabbits and guinea pigs. The concern has arisen because Pine is an aromatic softwood and the aroma is produced by chemicals called phenols. These can be inhaled by rabbits and are removed from their bloodstream by the liver. This puts a strain on the liver and it has been suggested that this can cause liver problems and interfere with the effectiveness of some drugs.\r