After 5 days of using Frontline Plus I gave my dog a good thorough bath because she was still itching and biting herself. The strange thing was, I saw no dead fleas coming off of her. Why were there no dead fleas not even 1? Also, is this true... if your dog is allergic to fleas your dog will have very little fleas to no fleas? I read a comment recently about dogs being allergic and it didn't make any sense, I thought if your dog is allergic to fleas it would be infested with tons of fleas uncontrollable amount. Is it true yes or no?