Contains Fipronil the active ingredient used in Frontline® - Top Spot for Dogs* Fast-Acting, Long-Lasting Kills Fleas Kills Ticks Kills Chewing Lice Waterproof Kills Fleas, Ticks & Lice Flea + Tick Defense for Dogs contains the active ingredient fipronil that effectively targets fleas, ticks, and chewing lice. Fipronil collects in the oils of the skin and hair follicles, and continues to be released from hair follicles onto the skin and coat, resulting in long-lasting activity. Fleas Kills adult fleas before they lay eggs Controls flea re-infestation for up to one month (4 weeks) Controls fleas which may cause flea allergy dermatitis Ticks Kills ticks that may transmit Lyme disease, Rocky Mountain spotted fever, ehrlichiosis, and babesiosis Lice Rapidly eliminates infestations with chewing lice Mites Aids in control of sarcoptic mange infestations