How Does Flea Treatment Work?

Pet owners are recommended to apply a flea treatment to their pet regularly in order to prevent infestation and to eradicate any parasites that are already living on their animal. But just how does flea treatment work? Here we look at the common ingredients of flea treatments and the method by which they work.

Common Ingredients In Flea Treatments

Although different flea treatments contain a variety of chemicals and plant extracts, here are some of the ones that are most commonly found in popular treatments.


Pyrethrins are chemicals which are produced by certain varieties of chrysanthemums. Having been used for centuries as an insect repellent and insecticide, these are now one of the most commonly found ingredients in flea control treatments for animals.

plant extracts

Flea treatments contains Plant Extracts

Pyrethrins work by altering the way an insect’s nerve cell functions. They cause it to fire non-stop impulses which eventually causes the insect to die.

One of the benefits of pyrethrins is that they are low toxicity and this makes them safe when used on mammals. This type of treatment is applied onto the skin or fur of the animal and it controls not just fleas but also other insects such as mosquitoes, mites, lice and ticks.

However pyrethrins are not used alone to combat fleas as they cannot stand up to long term exposure to moisture, air or light. They are therefore combined with different chemicals to stop them breaking down.

Many topical flea treatments contain the manufactured version of pyrethrins known as pyrethroids. These last for longer and are more stable so are used for the long-term spot on products and also in household sprays.

Plant Extracts

Flea treatments also contain other natural plant extracts that are flea deterrents, including rotenone, d-limonene, and linalool. Rotenone paralyses insects, preventing their cells from taking in oxygen. D-limonene and linalool soften insects’ hard shells which makes them dry out and die.


Imidacloprid blocks the conduction of the insect’s nervous system, usually within 24 hours of application. This tends to prevent them from laying eggs. When mixed with a carrier that is oily in texture, it can spread over the animal’s body, collecting in hair follicles and it will work for around a month to kill eggs, larvae and adult fleas.

Fipronil and metaflumizone are two other chemicals used in spot on flea treatments, with Fipronil being found in sprays too. Both chemicals target the function of the insect’s nervous system causing them to become paralysed and die.