Deflea rtu cat shampoo 8 oz. attacks the physical structure of the flea or pest by dissolving the waxy protective coating. The other active ingredient(primarily a laxative in laymens terms) is then able to penetrate the f. Apply deflea shampoo onto coat of pet. Work shampoo into pets coat until a lather forms. Treat the entire pet including hard to reach areas such as between paws. Rinse animal & dry thoroughly. Undecylenic Acid 8 OUNCE