Cat Flea & Tick Active Ingredients
Drs. Foster & Smith Educational Staff

Cat Flea & Tick Active Ingredients

There are more flea and tick products available today than ever before. Provided below is a brief description of the various categories of active ingredients found in today's flea and tick preventives.


Etofenprox: (Bio Spot® ACTIVE CARE SPOT ON® for Cats)
A pyrethroid, which is a longer-lasting, synthetic relative of natural pyrethrins. Kills and repels ticks, fleas, lice, and mosquitoes. Etofenprox is labeled safe to use on cats.

Fipronil: (Drs. Foster & Smith Fiprotrol™ Plus, Frontline Plus)
Blocks the passage of chlorine through cells in the insect’s nervous system, causing paralysis of the insect. Collects in the oil glands of the skin, then is slowly released. Water-resistant. Protects against ticks and adult fleas.

Imidacloprid: (Advantage II for Cats)
Interferes with the nerve conduction system of insects by blocking the insects’ nerve receptors. It kills fleas but does not have activity against ticks.

A plant-derived extract used in environmental flea and tick control. Affects the insect’s nervous system.

Pyrethrins: (Flea and Tick Shampoo)
A natural plant extract from the chrysanthemum flower. Provides quick flea and tick killing action with a wide margin of safety.

Sodium Lauryl Sulfate:
Detergent-like nontoxic flea and tick control.

Insect Growth Regulators

Methoprene, Nylar: (Drs. Foster & Smith Fiprotrol™ Plus, Bio Spot® ACTIVE CARE SPOT ON® for Cats, or Frontline Plus)
Mimics the natural juvenile hormone in insects that prevents the pupa from molting into an adult, thus breaking the biological cycle. Used in flea control products.