Commercial topical products such as Frontline, Advantage, K9 Advantix, and Revolution are, of course, formulated to control fleas. Each of them contains different chemicals, many of which are hazardous. (See the post about dangerous chemicals.) Some of these chemicals may be more effective than others in flea control.

A flea is a very resilient creature — difficult to control because it reproduces so rapidly, and difficult to kill because of its bodily structure. Can a flea build up a resistance to chemicals such as fipronil, a key ingredient in Frontline? Quite possibly. Evidence exists that insects can become immune to certain chemicals over time.

If you are using a commercial topical product like Frontline, be sure you are following the manufacturer’s application instructions precisely. If you suspect it is not controlling your pet’s fleas, you may, in certain cases, be able to reapply it in as little as two weeks and try again. Speak to your veterinarian about this first.

One alternative is to switch to another topical product. Another alternative is to supplement the topical product with another product that works internally, such as Capstar.

Based on the research conducted for our Flea Control book, however, we believe the best alternative is a natural one. We think it is safer and more effective to switch from commercial products with potentially unsafe chemical ingredients to natural products — products that nature designed to control fleas. For example, using predatory nematodes in your garden is one way to control fleas naturally outside your home. A way to control fleas naturally inside your home is to apply diatomaceous earth or salt to your carpet. A way to control fleas naturally on your pet is to use neem oil.

These natural substances have been proven effective for controlling fleas for a long time — longer than the chemicals that are used in most commercial flea control products. The natural substances mentioned here are just a few alternatives to chemical products — you’ll find others in the Flea Control book.

According to the Natural Resources Defense Council (NRDC): “Many Americans believe that commercially available pesticides, such as those found in pet products, are tightly regulated by the government. In fact, they are not. Many of the products sold in grocery, drug and pet supply stores, even when applied as instructed on the box, can cause serious health consequences to pets and humans. Just because these products are on store shelves does not mean they are safe.”

The EPA did ban six types of organophosphates from the pet products market because they were found to be extremely harmful to pets and children. The banned substances are: chlorpyrifos, dichlorvos, phosmet, naled, diazinon, and malathion. One organophosphate has not yet been banned: tetrachlorvinphos (TCVP). Be certain you avoid pet products with any of these ingredients. Carbamates, another dangerous class of chemicals, should also be avoided.

The NRDC offers the following advice:

Products with the following chemicals should be avoided:

Amitraz, fenoxycarb, propoxur, and tetrachlorvinphos (TCVP)

Products with the following chemicals should be used sparingly:

Fipronil, imidacloprid, metaflumizone, pyrethrins, selamectin

Products with the following chemicals are considered generally safer:

Lufenuron, nitenpyram, pyriproxyfen, s-methoprene, spinosad

Note that cats are particularly sensitive to the adverse effects of pyrethrins and pyrethroids (synthetic versions of pyrethrins). If products with these ingredients are used on dogs with cats in the home, cats can still be exposed to toxicity.

If you are planning to use ANY flea control product, it is advisable to read the label not just for warnings, but for a list of ingredients. Refer to the NRDC’s website, http://www.greenpaws.org, for detailed information about pet products with harmful chemicals. Download the handy toxic chemicals pocket guide (PDF) here: http://www.greenpaws.org/_docs/GP_pocketguide.pdf