Advantage flea control for cats, got it on the cats fur because he moved?

what if he can reach the area? its still back of the neck but it looks like the area is bigger now and i'm scared he may be able to ingest it somehow. the stupid dog brought fleas in. now im scared my cats may get sick. and how long does it take to dry? after asll this trouble i'm thinking whats worse this or the fleas?