A single dose of Capstar Oral Flea Tablets for Dogs starts killing fleas within 30 minutes and achieves greater than 90% effectiveness against adult fleas within 4 hours. Capstar kills adult fleas that may cause flea allergy dermatitis. Capstar Oral Flea Tablets treat flea infestations in dogs and puppies 2 pounds of body weight or greater and 4 weeks of age or older. It is safe to give as often as once a day if your pet gets re-infested with fleas, and can be given with or without food.