What are Fleas?

Adult cat fleas are reddish-brown insects with a body that is compressed from side to side. While visible to the naked eye, they are so small you could line about eight adult fleas end-to-end in one inch. Because fleas are so small, they can be difficult to detect, especially since cats have a tendency to groom them off and ingest them.

Fleas are wingless, but possess incredible jumping ability. This enables them to easily jump from ground level to “ambush” a pet.

Fleas feed on blood, and female fleas consume about 15 times their body weight each day2. This poses a threat of anemia to puppies as well as heavily infested or debilitated adult cats. Incompletely digested blood is excreted and dried to form what is commonly referred to as “flea dirt.” This serves as food for developing flea larvae and is one way veterinarians and pet owners can identify an infestation.

Why do they have to eat so much? They need nourishment to reproduce. In fact, adult female fleas may begin to feed on an animal within minutes of contact and actually begin to lay eggs within 24 hours. These eggs then fall off the cat and become larvae.

Learn more about the flea lifecycle

Why worry about fleas? 

Fleas can pose a serious problem for your cat's health.

Not only can fleas make your cat miserable, but depending on his age and overall physical condition, fleas can pose a serious threat to his health.

  • Fleas can cause severe discomfort for cats, including scratching, chewing, biting and restlessness.
  • Fleas are the source of flea allergy dermatitis (FAD), the most common veterinary dermatological condition3.
  • Severe flea infestations can cause anemia, especially in kittens or debilitated adult cats.
  • Ingested fleas also can transmit tapeworm infection to cats.

Fleas also raise human public health concerns.

Your cat isn’t the only household resident that can suffer from flea bites. Flea infestations in homes and areas around a home often result in humans being bitten by newly-emerging fleas. You, too, are at risk for health issues, some of which can be serious.

  • Allergic reaction: Usually in the form of small, raised lesions, called papules, that can be red to purple in color. Severity will vary, depending on the severity of the allergy to the flea bite.
  • Cat scratch disease: Commonly known as “cat scratch fever.” An infection transmitted by cat scratches or bites and causing a red, bumpy rash similar to those caused by allergic reaction. Can also have more serious effects on people with compromised immunity systems.
  • Tapeworm: Tapeworm (Dipylidium caninum) is generally spread through infected fleas found on both cats and dogs. Ingestion of infected fleas by children can result in tapeworm infection.
  • Typhus: A group of infectious diseases usually resulting in a sustained high fever (typhus fever), headache, delirium and sometimes red rashes. Two kinds are most commonly contracted from flea bites:
    • Flea Typhus. A type of typhus caused by Rickettsia felis, a bacteria first identified in cat fleas.
    • Murine typhus. Another bacterial form of typhus transmitted most commonly by rodent fleas but also by fleas found on cats.
  • Plague: Rodent fleas that can be acquired by dogs and cats in some areas might be vectors for (carriers of) bubonic plague, Yersinia pestis. These fleas might leave the host to bite humans.
  • 1. Elanco Animal Health. Data on File.
  • 2. 2005 Flea Guidelines, Flea control for dogs and cats, Advanstar Veterinary Healthcare Communications, sponsored by an educational grant from Merial
  • 3. Sousa, C.A., DVM, "Fleas, flea allergy, and flea control, a review," Dermatology Online Journal, http://dermatology.cdlib.org.


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Fast acting

Killed 98–100% of fleas within 12 hours1,2.

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