WHAT IS FRONTLINE SPOT ON? Frontline Spot On contains fipronil, a phenylpyrazole licensed for use as a veterinary medicine. Fipronil is not an organophosphate compound.FRONTLINE Spot On is the original flea and tick spot-on formula from FRONTLINE, first used by vets, now available without a prescription.Once applied, the treatment will protect dogs from fleas, ticks and lice ? use monthly all year round.Kills fleas on your pet within 24 hours. Kills ticks within 48 hours, helping reduce the risk of tick-borne diseases. WHAT IS FRONTLINE USED FOR? It kills fleas and ticks on your dog to help protect them from the discomfort and diseases these parasites cause. Use it every 4 weeks for optimal protection. Frontline Spot On is a treatment for both cats and dogs that provides long-lasting protection against fleas and ticks, and controls biting lice.