From what I have read on pet rat sites, the best treatment is "Revolution" for cats or kittens. Not sure how it compares to frontline, but it's supposed to be very safe for the rats and it stays in their system for 30 days so it breaks the 3 week life cycle of mites.

My adult rats are pets so I don't mind using such treatments on them. I have 2 males that are seriously mite infested. I didn't realize it was mites and it didn't seem so bad before, but it's pretty serious now. I've ordered Revolution and am just now waiting for it to get here in the mail from Australia. Requires a prescription here but apparently they can ship it from Australia without a prescription. 1 drop between the ears/back of neck and that should take care of it.

If you do have mites you should treat all the rats as they probably all have them, showing symptoms or not. If you only treat the ones showing symptoms the mites will just hang out on the others and re-infect the treated ones after the treatment wears off.

www.petshed.com