When a cat has diarrhea, the owner needs to treat the cat's diarrhea first, feed the cat medicine to treat diarrhea, adjust the cat's diet, buy roxithromycin ointment and apply it to the cat's anus to help reduce inflammation and relieve redness and swelling, and continue to apply it after the cat stops diarrhea. After a few applications of roxithromycin ointment, the cat's anus will return to normal. If the hair around the anus is stained when the cat has diarrhea and it is difficult to clean, you can use scissors to cut the hair short to prevent the cat's hair from getting feces.