Last night I gave my dogs their first dose of Comfortis of the year. Within minutes it started working and the darn things started jumping on me! First fleas I've had on me since last year, they kept jumping into my beard :/ I killed about 7 or 8 with my fingernails before the medicine killed all of them. Was really weird, it's like they knew it was all over and I was responsible. No more butt chewing, all of us are happier now. Except the fleas.