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How Long Does Frontline Take to Kill Fleas?

| Updated September 26, 2017

Frontline is the brand name of an internationally sold product line designed to stop the life cycle of fleas, specifically formulated for use on cats and dogs.


The active ingredient in all Frontline flea medications is Fipronil, which and works by storing itself beneath the skin, in the sebaceous glands. Frontline is secreted along with the natural oils of the skin, continuously killing fleas as they come in contact with the skin or hair.

Adult Fleas

Frontline kills adult fleas within approximately 18 to 24 hours of coming into contact with a treated pet, even if they do not bite the animal.


Fronline Plus is an all-inclusive flea elimination system, working to kill fleas at each stage of the life cycle--eggs, larvae, pupa and adult fleas on the animal, as well as four types of ticks.


Frontline has several different types of topical medications that kill fleas, Frontline TopSpot and Frontline Plus are pre-measured doses sold according to animal weight, and Frontline Spray, which is useful for quickly treating infestations.


Frontline Spray has not been regarded or approved as safe to use on animals that are nursing, pregnant, or if you plan to breed your pet while the medication is active.