Activyl spot on is a once monthly flea treatment for the prevention and control of fleas containing the unique active ingredient indoxacarb activyl flea treatment is perfect for treating your pet against unwanted fleas activyl is the only flea treatment to benefit from metabolic activation activyl will stay on your pet after swimming or exposure to water after 48 hours of the treatment being applied with its quick drying action and fragrance free smell activyl is the perfect flea treatment