Welcome to Cat Forum, and we'll try to help you and your kitty.
First are you sure it is fleas?
If it is, all it takes (for an allergic/sensitive cat
) is one bite from one flea to begin the allergic reaction and make the cat feel itchy and want to scratch...even through scabs and wounds. Have you seen any fleas on your cat? In your home? Around your yard? ...and finally, do you live in a known flea problem-area?
I have always had great results using Advantage and Revolution spot-on treatment products with my cats, in addition to treating the home. It sounds like what you have done and are doing, should be eliminating the flea problems properly. I mean, you can't do any better unless you call out the National Guard against the fleas! You shouldn't
be having a flea problem with the steps and precautions you've taken.
Next, may I ask what you are feeding the cat?
I apologize, I really do not mean to be insensitive, but most commercial cat foods that are purchased at the grocery stores and/or have budgets to purchase commercial air-time to market their product...really don't *have* the great ingredients they are telling you they do. Well, certainly the food meets the nutrition standards, but in order for these corporations to be able to *afford* all this air-time for advertising, the money must come from somewhere...and it comes out of the profit from selling product with 'cheap' ingredients.
There are *many* pets who are allergic to fillers like corn, carb-sources like wheat/rice and their protien (meat) ingredients are a little 'suspect' (lots of the left-over 'yucky' parts). In addition, it appears many cats are, or become intolerant of, fish and fish products which are used quite a bit in cat food to help make the food smell appetizing. Also, cats (and dogs) can develop these allergies suddenly.
I do not have a good working knowledge of cat nutrition, certainly not enough to guide you towards better and non-allergic-source products...but if you would take a general read through this site's Health/Nutrition forum you should be able to get some good ideas. Also, as the day goes on, more and more members who are more knowledgeable than myself will drop in and be able to add their information, too.
Best of luck to you and your cat,
PS...just wanted to say I did a little google of your siggie and found you at some other forums. It still didn't help me understand what your siggie 'means' , but that's okay. I'm certain it would be *beyond* me. Waaaaaaay beyond me.