Capstar is not a flea preventive, as it only kills adult fleas. It enters the bloodstream to poison the fleas that are already on a cat and biting it. It will do nothing for eggs or pupa fleas, which means that without doing anything else, you will soon be right back to where you started. It can be given to jump start an effort to get rid of fleas, but it won't prevent re-infection. When a vet prescribes it, it is usually given to cut down on the number of fleas in order to prevent flea-related anemia (which can happen when a cat is infested with fleas). You may chose to give Capstar to your cats, but you will have to treat the environment in conjunction with it, and it will still be tough going. Your cats may get re-infested very easily, as it only works for about 24 hours or so. Capstar will do nothing for ticks, ear mites and most parasites that a preventive covers for. Now Revolution, Frontline and Advantage are flea preventives. They basically change the chemical signature of a pet's skin to make it more unpleasant to fleas (this is why they are given topically). You still have to treat the environment to get rid of the fleas, but you have a little bit more leeway, as it will take between 24-28 days for something like Revolution to wear off. Revolution will also provide some worm prevention and ear-mite protection. The other two also do well as worm preventives, but don't cover ear mites. They do give pets tick protection, which Revolution does not (in case you were wondering). Hope that helps you make an informed choice.

If your cat is hiding and this behavior is relatively new, you may want to seek a veterinarian to make sure his behavior is not the result of a health issue. Cats tend to hide their illnesses (an instinct from when they were wild), so hiding may be your cat's way of doing this. Your vet can do an exam and a simple blood test to see if there are any issues going on. If he comes back with normal test results, it may be that this is just the way your cat's personality is. All animals are different and have different personalities. Even though you feel that you have given him a safe environment to live in and treat him well, he may just be a cat that is shy or scared by nature. The same as some people are more outgoing than others, this may just be the way that he is wired. It should be noted, though, that as time progresses he may come around. Take him to the vet to make sure this isn't a medical issue and continue to provide him with a safe, loving home.