Apparently Comfortis is no longer working on my Shih Tzu. It's working great on my Lab though! So, I put some Revolution from the vet onto Vida, the Shih Tzu and onto the kitten. This was yesterday about 4PM. Vida is still itching like a maniac (after a bath with Dawn...) and Mira, the kitten, after her bath still has fleas crawling all over her, INCLUDING directly on the site where I applied the Revolution. Does this stuff not work? How long does it take to come into effect?