From the Frontline website:
Few creatures can inflict more misery, ounce for ounce, than fleas. These tiny, almost-invisible pests can make life miserable and disrupt your household with a vicious cycle of biting and scratching. Fleas may also cause flea allergy dermatitis in some pets and may be carriers of dangerous diseases. All FRONTLINE products offer control of fleas, killing up to 100% of adult fleas on your pet within 18 hours. And with an added ingredient to kill flea eggs and larvae, FRONTLINE Plus completely breaks the life cycle of these dangerous and annoying pests.
Often too tiny to be seen, ticks attach to pets and feed on blood until they are engorged. They thrive in high humidity and moderate temperatures, but can be found all over the country. Ticks may carry and transmit diseases, including Lyme disease, that can cause serious health problems for pets and people. FRONTLINE Brand flea and tick control kills up to 100% of ticks on dogs and cats within 24-48 hours.