Cats can develop three main types of allergies: Flea, environmental, and food allergies. Flea issues can cause the cat's back and tail to be irritated. Vomiting, and diarrhea in addition to itchy skin on the face and neck, can all indicate a food allergy. Finally, environmental allergies can be caused by any pollen, perfumes, or smoke that the cat inhales; those are the ones to pay attention to while choosing a type of litter. Some of their symptoms include sneezing, coughing, wheezing, excessive licking, infections, etc. If one of your cats suffers from allergy problems, they will probably find some kind of litter less appealing. In this case, you'll need to look into different available options. There are many brands of organic cat litter which contain no chemicals whatsoever. These kinds of products are made using only natural materials. Natural litters are the best options for your allergic cat.