Can Boric Acid Kill Fleas?

By PetMD Editorial on May 6, 2016

By Aly Semigran

When it comes to eradicating fleas, pet parents will look for any safe and efficient method. Products containing boric acid are often used to kill insects, including fleas, but they must be EPA-approved in order to ensure they are safe for pets.

What Is Boric Acid?

Boric acid is derived from the element boron, according to gardening expert and You Bet Your Garden host Mike McGrath.

Robert Daguillard of U.S Environmental Protection Agency notes that boron, which occurs naturally in the environment, is an essential nutrient for many organisms and plants. Boric acid and its sodium salts, says Daguillard, are also present as inert ingredients in pesticide products and as ingredients in non-pesticide consumer products such as antiseptics and lubricants.

Boric acid is usually found in the form of crystals or white powder that dissolves in water.

Does Boric Acid Kill Fleas?

Yes, boric acid can kill fleas. “Boric acid and its sodium salts can kill insects by acting as a stomach poison or by abrading the exoskeletons of insects,” says Daguillard. In fact, he notes that one of boric acid’s first uses when it was registered in 1948 was to eradicate fleas.

Alicia Leytem, a pesticide specialist at Oregon State University’s National Pesticide Information Center, explains that boric acid can be used to kill cockroaches, termites, and ants because they eat the acid. When it comes to fleas, things work a little differently.

Larvae scavenging for a food in a carpet may ingest the boric acid and die, says Leytem. But more commonly, since adult fleas only feast on blood, they will not eat or ingest boric acid. 

Boric acid is most effective as part of an integrated flea control program, not when it is used alone.

How to Use Boric Acid To Kill Fleas?

First things first, you should be using an EPA-registered boric acid product.

Leytem warns that using boric acid by itself, or as a homemade concoction, could lead to problems. “The concern with homemade pesticide mixtures is that they don't come with directions on how to use them (where to apply them, how much to use, etc),” she says. “This could lead to someone possibly using much more than is needed (increasing the chance of an unintended overexposure), or applying it somewhere that could be more risky for people or animals.”

These EPA-approved boric acid products, which undergo risk assessments to avoid harm to humans and animals, are applied to floors and carpets, Daguillard notes. “They are worked into the fibers of the carpet or into cracks and crevices of the floor and left for a period of time,” he says. “Some are also labeled for use on upholstered furniture.”

Leytem explains that boric acid should not be used outdoors because if the substance gets wet, it may no longer be an effective flea treatment.

“Because it’s a pesticide, it’s intended to kill something. All pesticides have some level of toxicity,” Leytem notes. That’s why following the directions from EPA-registered boric acid products is essential for both pet and human safety. Boric acid should never be applied directly to your pet.

Should You Use Boric Acid Products to Kill Fleas?

You can, but McGrath points out that products with boric acid aren’t necessarily the cheapest option, nor the easiest to come across. “Diatomaceous Earth is a much better choice for desiccating, and easier to find,” he suggests.

McGrath explains that vacuuming, grooming and light traps are often better natural responses to a flea problem.

Is Boric Acid Safe for Pets?

By following the rules and directions of EPA-approved boric acid powder products in your home, you, your family, and your pets should be safe.

“[Boric acid] is considered practically nontoxic to birds, fish, and aquatic invertebrates,” says Daguillard. “For birds and mammals, risk is primarily associated with the granular formulations and bait uses.”

According to the U.S. National Library of Medicine, poisoning can occur if a pet or human swallows powdered products containing the chemical. Chronic poisoning can happen when pets and humans are repeatedly exposed to boric acid. Symptoms of boric acid ingestion can range from vomiting and diarrhea to seizures. Call your veterinarian if you think your pet may have ingested boric acid.

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