DERMA-IONX has been helpful in flea allergy dermatitis. As for dosing DERMA-IONX, I prefer to give 10 drops onto some canned food twice daily at breakfast and supper. After there is some improvement I switch to a whole dose once a day. I also give probiotics, and Omega 3,6,9. Vetionx carries all of these. If your water contains chlorine, give filtered water instead. Chlorine is damaging to the intestinal flora. According to Chinese food therapy, choosing a cooling food such as fish or turkey should help. I would look for a grain free version. I have had good results with Purina's grain free Beyond white fish flavor. I would give a food without grains until the skin is healed.
I would also suggest that your cat be checked for internal parasites(with a stool sample) if it hasn't been done recently. Worms have a negative impact on the skin and coat. Cats often acquire tapeworms when they get fleas.
Please let us know if you have any other questions.