Sergeants flea medicine reaction?

My dog had reaction to flea medicine i called the hotline and they described his symptoms exactly. They said bath in in dish soap. I have now its 4 days later and he is still scratching and he kind of has a tic i guess. He jerks his head to the left like a twitch or something. Hotline number said he probably feels the itchy feeling and is trying to bite at it. Should i take him to the vet?