hi there, i am treating my boy for mites with "Spot on" which contains ivermectin and it seems to have done the job. it was only Â£3.99 (about $5) from the pet shop and it comes in 4 pippets. use one pippet for a rat and put it on his neck and rub over him. i kept him distracted so he didn't stratch it off until it had dried. i have noticed where he was itching under his chin that it has a lump so i am going to wait one or two days to see if it goes down as i am hoping it is just irritated from scratching as he stopped scratching straight away.