Lufenuron is the active ingredient

Active ingredient

An active ingredient is the substance of a pharmaceutical drug or a pharmaceutical ingredient and bulk active in medicine; in pesticide formulations active substance may be used. Some medications and pesticide products may contain more than one active ingredient...

 in the veterinary

Veterinary medicine

Veterinary Medicine is the branch of science that deals with the prevention, diagnosis and treatment of disease, disorder and injury in non-human animals...

 flea

Flea

Flea is the common name for insects of the order Siphonaptera which are wingless insects with mouthparts adapted for piercing skin and sucking blood...

 control medication Program, and one of the active ingredients in the veterinary flea control, heartworm

Heartworm

Heartworm is a parasitic roundworm that is spread from host to host through the bites of mosquitoes. The heartworm is a type of filaria, a small thread-like worm. The definitive host is the dog but it can also infect cats, wolves, coyotes, foxes and other animals, such as ferrets, sea lions and...

 prevention, and anthelmintic

Anthelmintic

Anthelmintics or antihelminthics are drugs that expel parasitic worms from the body, by either stunning or killing them. They may also be called vermifuges or vermicides .-Pharmaceutical classes:...

 medicine milbemycin oxime/lufenuron (trade names Program plus, Sentinel Flavor Tabs).

Lufenuron is stored in the animal's body fat

Fat

Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

 and transferred to adult fleas through their bite

Bite

A bite is a wound received from the mouth of an animal, including humans.Animals may bite in self-defense, in an attempt to predate food, as well as part of normal interactions. Other bite attacks may be apparently unprovoked. Self inflicted bites occur in some genetic illnesses such as...

. Adult fleas transfer it to their eggs by its presence in the mother flea's blood, or by the larva feeding on pre-digested blood

Blood

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

.

Lufenuron, a benzoylurea

Benzoylurea

Benzoylureas are chemical compounds best known for their use as insecticides. One of the more commonly used benzoylurea pesticides is diflubenzuron. Others include chlorfluazuron, flufenoxuron, hexaflumuron, and triflumuron. Lufenuron is the active compound in flea control medication for pet dogs...

 pesticide, inhibits the production of chitin

Chitin

Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...

 in larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

l fleas.