A previous poster said that Advantage and Frontline don’t work well. Nothing could be further from the truth!!! They are by far the best flea control. However, they should be administered outdoors as any fleas on the cat will leave in a hurry and could survive in the house. After a short period of time it’s fine to bring him back inside. As to him wanting to be by himself, let him, it’s a cat thing. Also, if money is a concern simply buy the flea control for a large dog and use a plastic syringe to measure out and administer the proper amount for a cat his weight. (Google it). That’s what my vet-tech friend did. The products are virtually identical for cats and dogs.