CrossBlock II is a topical medication that treats and prevents flea infestations on cats and kittens 8 weeks of age and older. Kills adult fleas as well as their eggs and larvae. Starts killing fleas within 2 hours and continues to work for one full month of protection. CrossBlock II also prevents re-infestation of fleas by breaking the life cycle and preventing fleas from reproducing. TOPICAL FLEA **no tick** NO EXAM REQUIRED.