Capstar is a quick action oral flea treatment for cats. The fast-acting adulticide controls adult fleas on cats and protects them from flea infestation. Highly recommended for heavy flea infestation, Capstar also treats flea allergy dermatitis in cats. Regular treatment with this oral flea control decreases the number of flea bites experienced by your pet. With its rapid and prolonged action, Capstar starts killing fleas within 30 minutes and works for 24 hours thereafter.