Once you have posted a few more times you should post your question in the 'Health & Nutrition' section. You'll get much more help there for sure.
It sounds to me like a food allergy, just from the little bit of description you gave that's a best guess.
Before you can post in the other section there are some basic things to rule out. You said you've tried many foods, were they all from the vet's office? The reason I ask is because you need to find a food that has no grains in it, but especially not any corn, wheat or soy. Those are the most common allergens for cats.
I'd suggest something like Natural Balance Green pea and Duck, or one of the EVO formulas (not chicken!). Switching to a good quality wet food, like one of the brands I've listed, may also help by adding more moisture to your cat's diet (and therefore to their body).
Personally I would also check all your cleaning agenst and try to pare it down to as little as possible. I use mainly white vinegar mixed with water, and orange TKO mixed with water. Many chemical cleaners can be very irritating to cats, so if it truly isn't a food allergy (unlikely, IMO) it's likely a cleaner.
Good luck and welcome!