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Fleas: Treatment & Prevention

Fleas: Treatment & Prevention

If your dog or cat is itching and scratching, fleas are a likely culprit. Flea season usually begins in spring and lasts through the summer into early fall, but fleas can survive year round in western Oregon's moderate climate.

Flea bites can cause local skin irritation and swelling that may cause your pet discomfort. Some dogs and cats develop an allergic reaction to flea bites, resulting in scratching, which can lead to hair loss or to a bacterial skin infection known as "hot spots." Fleas can host tapeworms, and can transmit bacteria, viruses, and protozoa.

Fleas that live on your pet can also infest opossums and raccoons, which can be important sources of flea infestation hot spots outdoors. Therefore, it's important to treat both your pet and your pet's environment. A flea control program is most effective when you treat your pet, your living areas, and your yard at the same time.

Flea Life Cycle

Depending on the climate and the availability of a host, the length of a flea's life cycle is variable. The female flea can lay up to 2000 eggs in her lifetime. The eggs fall off of the animal, which acts like a “living salt shaker” of flea eggs. Between 1 and 10 days later, the eggs will hatch into larvae in the environment. Larvae live anywhere from 5 to 11 days before they become pupae.

Pupae are difficult to eliminate, as you must wait for them to develop into adults before treatment will be effective. This stage is resistant to extreme environmental conditions, as well as chemical interventions that may be applied to the environment. It may take anywhere from 7 days to 14 days for pupae to develop into an adult flea; however, their emergence is largely dependent on heat, humidity, physical stimulation, and carbon dioxide from exhaled breath. Depending on these external factors, the pupae may “hatch” from their cocoon in 14 – 180 days and maybe even longer!

Once they emerge, an adult flea may live on a host up to 120 days. Fleas rarely jump from host to host. During peak flea season, the life cycle is about 3 weeks. At any given time, less than 5% of the flea population is adults, so it's important to treat your pet, home and yard for all stages of the flea life cycle.

Signs of Infestation

  • Adult fleas on your pet's skin or in your house.
  • Flea excrement (dark specks that turn reddish in water), also called “flea dirt,” on your pet's skin.
  • Irritated skin or excessive itching, which can lead to hair loss or a bacterial skin infection known as "hot spots."
  • Flea eggs (white oval shapes the size of table salt crystals) hung up in your pet's coat .

Treating Your Pet

There are several treatment options, including:


An adulticide, such as a topical monthly-use product, is applied directly to the pet's skin, where it is toxic to adult fleas, providing quick relief. Some oral tablets can be administered up to once a day or once a month.

Insect Growth Regulator (IGR)

An Insect Growth Regulator (IGR) is found in combination with some topical adulticides. IGRs do not kill fleas but do kill eggs and larvae to break the flea life cycle.

Insect Development Inhibitor (IDI)

An Insect Development Inhibitor (IDI) can be administered orally on a monthly basis or every 6 months by injection. An IDI keeps flea larvae from maturing to the next life stage, which also breaks the life cycle.

Integrated Flea Control

If you are experiencing an infestation, your veterinarian may suggest using both an adulticide and either an IGR or an IDI. This is called Integrated Flea Control and serves to rid your home of an infestation more rapidly.

Flea shampoo, dip, spray, combing, collar

These can be effective temporarily, but generally do not yield lasting results.

Treating Your Pet's Environment

  • Treating your house, garage, yard and kennel is another important step in controlling fleas. For best results, treat your living areas and yard on the same day that you treat your pet.
  • “Critter-proof” your yard by identifying sites in the yard that pets or wildlife may use as shelter. These include crawl spaces, areas under deck, porches, stairs, shrubs, or trees. Prevent access to any of these areas if possible. This is much more effective long-term, rather than trying to treat the outdoors, as these treatments only address 5% of the flea population or “the tip of the iceberg.”
  • Regular vacuuming and steam cleaning helps remove flea eggs, larvae, and pupae. Don't forget to dispose of the vacuum bag, as fleas can hatch in the bag after vacuuming.
  • A self-directed spray that will kill flea eggs and larvae in addition to adult fleas is the best choice for treating your house, garage, yard and kennel.
  • If you must treat your yard, a pet-friendly lawn granule application that will kill flea eggs and larvae in addition to adult fleas is best.
  • Foggers aren't able to treat underneath objects that fleas love to inhabit, such as couches, so it's best to use a spray to reach under those items.

 A Warning for Cat Owners: Use Flea & Tick Products Safely

  • Flea treatments meant for dogs can be deadly if given to cats instead. It is important to use only flea and tick products specifically designed for cats, and to administer the proper dosage.
  • Never apply 45-65% permethrin "spot-on" products to cats, even in small amounts. Highly concentrated permethrin can be extremely toxic to cats.
  • If you have both dogs and cats in your household, you should be aware that using a permethrin "spot-on" product on a dog may cause illness in a household cat.
  • All flea/tick "spot-on" products—even ones with nearly identical brand names—are not alike. Check the label to identify the active ingredient before you apply it. Carefully follow all pesticide label instructions.
  • The Pet Poison Helpine has provided more information about the safe use of "spot-on" products.

Your Veterinarian Can Help

Consult your veterinarian if you have questions about the safe use of flea and tick control products. Your pet’s good health is your veterinarian’s primary goal, and he or she will prescribe, administer and monitor the proper medications to achieve that goal.

If you are thinking about buying your pet’s flea control medications from another source (online or mail-order), you may want to consider these issues first.

Updated: May 2, 2018