DERMA-IONX has been helpful in feline allergies. As for dosing DERMA-IONX, I prefer to add 10 drops onto some canned food twice daily at breakfast and supper. If you need to you can give another 10 drops orally at bedtime. I also give probiotics, and Omega 3,6,9 to improve digestion and reduce inflammation.
Feeding a grain free diet would be wise at this time. The best flavors would be fish or turkey. According to Chinese food therapy these are more cooling than chicken or lamb. Beef is neutral. With allergies the body is more warm and so choosing foods that are cooler is better. If you think your cat is allergic to a protein do not give it. If you give your cat any treats please check the label. It is not easy to avoid chicken in a cat's diet.
If your water contains chlorine offer purified water instead.
I would also suggest that your cat be checked for internal parasites if it hasn't been done recently. Bring in a stool sample to your veterinarian so it can be checked. It would also be good to use a fine tooth flea comb to check for any flea debris in the coat. Please keep us updated on your progress.