When your dog or cat is suffering from dreaded adult fleas, you ll want to ease their itch right away. Capstar has a rapid-acting formula that delivers fast relief from fleas. Within 30 minutes of swallowing, Capstar starts knocking down adult fleas. Within 4 hours, 100 percent of fleas are dead. Best of all, Capstar doesn t leave a sticky chemical residue on your pet s coat and swimming or bathing your dog will not affect product efficacy. You only need to use Capstar when your dog or cat has adult fleas. Before you know it, they ll be flea free and feeling much more comfortable.