Experts advise to wash the litter box on a regular schedule to eliminate odour that could be building up in the box — some urine and feces can get stuck to the sides or bottom, says Dr. Coates. "Thoroughly washing and then disinfecting with a bleach solution physically removes waste and kills bacteria, keeping smells and illness-causing microbes to a minimum," LaFontaine said. "If you have clumping litter, clean at least once every two weeks. If you have traditional non-clumping litter, aim to thoroughly wash and dry the pan once a week." Dr. Barrack also recommends cleaning the scooper whenever you clean the box.