Cats will touch their urine on their hind legs when defecating, so the hair on their hind legs will turn yellow and cannot be washed away. At this time, the owner can feed the cat pet lecithin and egg yolk to help the cat nourish the hair and keep it healthy. The hair grows rapidly and replaces the yellow hair; if the owner wants to quickly remove the yellow hair on the hind legs, he can shave the yellow hair and wait for it to grow back.