Frontline Plus is a topical flea and tick preventative for dogs and cats. Frontline Plus kills 100% of adult fleas on your pet within 12 hours and 100% of all ticks and chewing lice within 48 hours. Frontline Plus has 2 tough killing ingredients. The 1st, fipronil, kills adult fleas and ticks. The 2nd, (S)-methoprene, attacks flea eggs and larvae. Frontline Plus is now recommended to be applied every 21 days, or every 3 weeks.