I have been using a well known brand of corn based litter.But noticed even when it got slightly damp it turned green then black... My cat started not using it, peed elsewhere and had high anxiety...So I am not a fan of the clay so only choice left was the paper litter..Lo and behold he went and peed in it immediately. Have 2 cats with 6 boxes...Left a little of the corn based for the other cat but at least I gave the cat a choice and he seems so much happier.... Corn based litter I believe is causing his excessive itching and cleaning.Did go to the vet she didn't know. Did food elimination did not work....ITS THE LITTER and the corn..Esp it turns black so fast even in slight dampness....Just started this trial but for a cat to jump in the litter so fast and use it says something..Its going to be more work but I'm out to please my cat not myself