Frontline Shield Extra-Strength Dog Flea and Tick 3-Dose Treatment is a fast-acting, monthly topical that provides 30-day protection against fleas, ticks, and mosquitoes. It not only kills fleas (plus their eggs and larvae) and ticks, but also repels ticks that may carry Lyme disease and mosquitoes that may transmit heartworm, helping keep small dogs safe from biting pests. Available in Multiple Weighted Dog Options and Sizes