Managing Fleas in Your Home

Philip Dickey is the household toxics coordinator for the Washington Toxics Coalition.

At one time or another, almost all dog and cat owners have to deal with fleas. Tormenting our furry friends and humans as well with their annoying bites, fleas can inflict more serious damage. They transmit tapeworms and several human pathogens, and they may cause allergies in both animals and humans.

West of the Cascades, where winters are mild and homes are relatively damp, fleas thrive unchecked by annual freezes. Many pet owners have resorted to purchasing a veritable arsenal of flea killers out of frustration and sympathy for their scratching pets.

Impregnated flea collars, insecticidal powders and shampoos, and aerosol bombs may endanger pets and other household members. And even these drastic measures do not provide permanent relief; the fleas always come back.

Successful home flea control is based upon knowledge of the fleas’ life cycle, periodic monitoring of the population, and a set of control methods. The idea is simple. First you decide at what level a flea problem becomes unacceptable to you.

Depending on your sensitivity and tolerance, this level could be the discovery of one flea bite per week, or finding two fleas each time you comb your pet. During the year the flea population will fluctuate. When the symptoms reach an unacceptable level, you apply control measures, beginning with non-chemical controls.

If stronger controls are needed, use the least toxic chemicals first. As soon as the symptoms recede, discontinue the chemical controls. In this way you can minimize the need for chemical controls. Before we discuss control methods in detail, let’s look at the flea’s secrets of survival.

The flea species found in most of our homes is the cat flea, even on dogs and humans. There are dog fleas and human fleas as well, but they are less common. All fleas have the four stages of development: egg, larva, pupa, and adult.

In the case of the cat flea, optimal conditions are a temperature of 65-80 degrees Farenheit and a relative humidity of more than 70 percent. Dry conditions are actually fatal to larvae. A female flea can lay 25 eggs a day for at least three to four weeks, up to 1,000 eggs during her lifetime. Although some eggs are laid on the host, most are found in bedding where the pet sleeps and in floor cracks, rugs, furniture, and dust.

In two to 21 days, tiny worm-like larvae hatch out, feeding for nine to 200 days on dried blood feces from the adults. Finally the larvae spin a cocoon in which they transform into pupae.

Hidden in the cocoon for seven days to a year, the pupae remain dormant until they hatch out in response to detection of a host. Immediately upon emergence as adults, the fleas bite the host to obtain blood. If necessary, adults could actually go for a month or two without food, and with a single meal they can survive for eight months.

These wide variations in development times for the various life-cycle stages explain why so many adult fleas can suddenly emerge when conditions are right. The fleas have actually been there all along, but they do not mature until late summer and fall when temperature and humidity increase to favorable levels.

At any given time, fleas may exist in all four life-cycle stages in your home. Control procedures must address all four stages. The program described below is aimed at killing or removing adult fleas on the host and eggs, larvae, and pupae found off the host. In order to succeed, this program must be followed exactly as described, utilizing the physical controls first and the chemical controls only if necessary.

Fleas tend to accumulate where your pet sleeps. Establish one regular sleeping area for your pet in a place that can be cleaned easily and regularly. This is easier for dogs than for cats. With cats you may have to place removable cloths in several places where they like to sleep. Bedding materials such as blankets or nearby rugs should be removed frequently and washed.

Vacuum every week with a strong agitator-type machine all areas to which your pet has access. Be sure to use a crevice tool for out-of-the-way places, and don’t forget the upholstered furniture. During “flea season” in the late summer and fall, you may need to vacuum more often, every third day or so.

Material collected by the vacuum must be removed from the house and disposed of right away. Severe flea infestations may require an initial shampooing or steam cleaning of rugs and upholstered furniture.

You can reduce the spread of fleas by keeping pets out of certain rooms in the house, particularly bedrooms or rooms that are difficult to clean, such as basements and attics. Pets should also be kept out of rooms belonging to family members who are particularly susceptible to flea bites. In severe cases, keep animals either outside or inside, but don’t let them go back and forth.

Flea traps can also be used indoors. They use a small light bulb to attract fleas to a piece of sticky paper. These traps can reduce flea populations, but they will not eliminate a flea problem by themselves.

Two techniques can remove adult fleas from the pet itself: combing with a special flea comb and bathing the animal. Combing is especially useful for cats, which generally dislike being bathed. A flea comb has specially designed metal tines spaced to allow hair but not fleas to pass through.

Flea combing should be done outdoors, just before your pet comes back inside, or in the bathtub. As you run the comb through your pet’s fur, some fleas will jump away, but others will stay on the comb. Remove the fleas from the comb and drop them into a nearby container of soapy water, which can later be flushed down the toilet.

Shampooing an animal knocks some fleas off and drowns others. It can be especially useful to reduce a heavy infestation. Ordinary soap or shampoo will work to a degree, but an insecticidal shampoo such as those described below is more effective. Be sure to wash the animal thoroughly, keeping the soap away from its eyes. Discontinue using any product that produces skin irritation or allergies.

The safest chemical we know of for killing fleas is an insecticidal soap. Safer, Inc. makes a soap for treating the pet and its surroundings. Safer also makes an indoor/outdoor pump spray called Pet and Premise, in which a small amount of pyrethrum is added to the soap.

Pyrethrum is a naturally-derived insecticide which is toxic to humans, pets, and beneficial insects, but the extremely small amount in this product does not pose much risk to mammals. Many other pyrethrum-based products are available, but cat owners should be careful because cats are especially sensitive to pyrethrum. Pyrethrum breaks down rapidly in sunlight, so its effect is short-lived. Use exactly as directed on the label.

Next after soaps, the safest chemicals to kill adult fleas have been thought to be the citrus extracts limonene and linalool. Natural constituents of lemon peel oil which are used as food flavorings, both of these compounds are quite toxic to adult fleas and relatively non-toxic to vertebrates.

There has been some concern about limonene, which causes tumors in male rats, though not in mice or female rats. It is not clear that there is a risk to pets or humans. Until this issue is clarified, you may want to avoid products with limonene, or at least those with a large amount, such as some pet dips or concentrates.

Always follow label directions to be sure you are using the product properly. Repeat applications may be necessary, especially if the product kills only adult fleas.

Methoprene is an insect growth regulator that mimics natural insect hormones and disrupts certain growth processes in the insect, preventing immature fleas from becoming adults.

It is supposedly quite specific to the target insect and of low toxicity to mammals, but recent concerns about the ability of synthetic chemicals to disrupt hormones in humans may prompt a re-evaluation of methoprene. Methoprene does not kill adult fleas, however, so it must be used in combination with other controls.

The most effective time to use methoprene is when flea populations are just beginning to build. Wait for signs of a rising flea population before treating.

Methoprene is available to consumers in aerosol foggers and as a concentrate. We do not recommend the use of foggers, even those with methoprene as the active ingredient. Some foggers contain toxic solvents as inert ingredients.

If your flea problem is serious enough that you feel you may need methoprene, use it only as directed or consult a reputable professional. Pyrethrum can be used with methoprene to kill adult fleas, but beware of mixtures of methoprene with much more toxic insecticides.

Dessicants kill fleas by drying them out rather than by poisoning, so they are less hazardous than many insecticides, but they are still not without some risk to humans. Diatomaceous earth, a fine mineral powder, is hazardous if inhaled. Boric acid, a moderately toxic chemical with possible reproductive effects, can be particularly dangerous to infants; a lethal dose may be as little as one-fifth ounce.

Some pest control companies now apply boric acid powder to carpets, guaranteeing no fleas for one year. While we know of no illnesses related to this process, boric acid is readily absorbed through cut or abraded skin and the dust can be inhaled.

Parents should keep toddlers or children with cuts or skinned knees off of treated carpets and should be diligent about vacuuming any dust they observe. With those precautions, the boric acid treatment may represent a good solution in many cases, especially severe infestations.

We do not recommend chemical flea control in the yard because pesticides can kill beneficial soil insects, as well as bees and birds. A better approach is to apply beneficial nematodes, tiny worms that infect and kill flea larvae.

Nematodes are available under the trade name BioSafe. They are quite effective if applied once soil temperatures reach at least 55 degrees Farenheit. Nematodes will die if the soil is not kept moist. A side benefit is that nematodes also help control craneflies and root weevils. Read the label for specific directions.

Recently, a number of new flea control products have become available from veterinarians. One is taken internally by the pet and kills fleas from inside. Another is applied to the fur, usually on the back of the neck. The big advantage of these approaches is that they are very targeted applications and require little effort.

They are reported to be quite effective at controlling fleas on the pet, but will not kill fleas already in the carpet. If you are concerned about possible toxicity to your pets, consult your veterinarian as you would regarding any other medication. Some people recommend discontinuing these treatments during the winter when fleas are not as active. u

This is an abridged version of a more extensive fact sheet available in print form from Washington Toxics Coalition. For more information, visit their web site (www.watoxics.org). Print versions can be ordered from Washington Toxics Coalition either over the Internet or by calling 800-844-SAFE.