How Long Does It Take For Flea Med To Work. It may take another dose or two or more of the medicine to fully break the flea life cycle. The majority of flea products eliminate adult fleas and stop them laying eggs, but none work immediately.
How long does it take for frontline to work? Oral medication treatment how long until effective 30 minutes. Revolution is given monthly so don't give it any sooner than that unless the vet says it's ok to do so.