They are very pure and would be really really careful on how you use them. After using an alternative remedy repelling mice (peppermint oil) I completely agree with pebble, my reply above I dont think was clear enough, you should not go messing about with essential oils on guinea pigs and only use items that are specific and tested safe for use on guinea pigs. mine did not like the smell in their room (it did them no harm and did expel the little blighters), only two rooms in my house have air freshners and they are not near to the pigs.