Hi I took my Guinea pig which I bouight from Petco... big mistake because at the time I did not know that there are so many rescue shelters that have guinea pigs who need homes... so anyway I had the guinea pig for less than than 2 weeks and I had him in my lap and started to look at his ears just to make sure that they looked clean. They didn't, in fact , they looked pretty dirty to me, although I have never looked in a guinea pigs ears before. So I called Petco and they took him to the vet . I was told by the Petco associate who took the guine pig in that the vet did a mircoscopic test and did not see anything such as mites, bacterial infection... etc . However the associte told me that the vet did give the guinea pig a one time ointment application called revolution just in case the guine pig did in fact have ear mites... I also had purchased a baby guinea pig the day before this event of noticing the dirty ears in my guinea pig. So thery were only togther in the same cage for litewrally 10 hours. So here is my question / problem : If my Guinea pig tested negative for ear mites but the vet gave him a preventive dose than do I still have to separate the baby guuinea pig from the other one ? I would think not because the test was neagtive, But I don't know! Im very confused! Does anyone have any info or knowledge about this?