The cure to flea allergies is getting rid of the fleas. If you are using over the counter flea treatment that isn't working, you may need to go to a vet to get flea meds that are different, however, most of the frontline type meds are over the counter now. Fleas can build up a resistance though to a certain med which means you need different or stronger stuff.
If it were my dog, I'd treat the environment, check the med I gave her against other stuff like frontline or advantage (which are over the counter in many places) and see how things go.
If things aren't going well in a two weeks, or if she is looking very inflamed, you may need a vet.
If you suspect secondary infection, antibiotics or topical steroids might be prescribed, but the number one solution to flea allergies is getting rid of the fleas on the animal and in the environment.