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Toxic effect of boric acid on animals


Q. What will boric acid do to animals? Is it harmful or deadly?

Juanita Oakes
- Little Rock, Arkansas


A. Hi, Juanita. I would guess that boric acid at the right concentration will clean animals' eyes like human eyes, rather than harm them. But if they gobbled it down, and whether they would do so, I don't know.

Please try to give us the scenario you envision. Thanks!

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Ted Mooney, P.E. RET
Pine Beach, New Jersey

Boric Acid Powder


A. Home made roach killer made from boric acid [linked by editor to product info] and whatever typically will cause a cat or dog to froth at the mouth and possibly barf. It is possible for an animal to die from it, but not very probable. Two cats and one small dog have lived thru it quite nicely, but it sure made a mess on the rug. Typical additives like sugar, condensed milk, peanut butter and bacon dripping will be eaten by animals if they can get to it.

James Watts
- Navarre, Florida


A. Here is a link to some info published by the National Cotton Batting Institute about the safety of Boric Acid. Turns out, the toxicity is somewhere between Aspirin and Table Salt. Also they state, "It is important to remember that there have been no known deaths resulting from the use of boric acid or Boron No. 10 in mattresses or upholstered furniture or even in their use as an insecticide."

Nicholas Jankowski
- Baltimore, Maryland

Ed. note: That link no longer works, but we thank Nicholas for showing us the good way to provide an internet link: with a brief summary of what it says, so that when it breaks (which they usually do quickly) the response still has value. Plus, if someone wants to search for a new address for the link, they know what they're looking for. Thanks!


Q. Hello,
Most recently my calico kitten has attracted a type of eye infection. I am concerned that it is spreading to her other eye. Please help. I have purchased a bottle of Boric acid powder. I have heard that applying boric acid will stop the infection from spreading and help the healing progress. Please notify me as soon as possible to inform me if this is true and will help my kitten or if it will kill her. I will be greatly in your debt.
Most graciously;

Mari-Alice Jasper
- Pembroke, Kentucky

A. Hi, Mari-Alice. It may or may not be the best treatment for her eyes, but a boric acid eye treatment certainly won't kill her.


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Ted Mooney, P.E. RET
Pine Beach, New Jersey

July 28, 2008

A. Use regular eye drops on your kitten. its much safer and it cleared up my son's kitten over night.

Vera L Taylor
- Taylor, Florida

Cat Owner's Home Veterinary Handbook

March 20, 2012

thumbsdownYes, Boric Acid is most certainly a toxic danger to Cats and can kill the cat if it is ingested.

I just had a tragic experience with this after a kitten I adopted out to someone stupidly treated his carpets with Boric acid and LEFT it in the carpet without vacuuming it up. The cat inadvertently ingested some, and it did kill her.

Forget the misinformed persons who keeps saying that Boric acid won't kill a cat, it most certainly can.
There are safer alternatives to employ that don't involve possible death.

See actual scientific info here:

Stacey Gardner
- catskill, New York, U.S.A.

March 21, 2012

Hi Stacey. Sorry about your cat, but that 'actual scientific info' page starts off dead wrong with "What Is Borax? Borax is also known as boric acid" :-)

Borax is Na2B4O7.10H2O, boric acid is H3BO3.

According to "Boric Acid/ Borates/ Borax Beyond Pesticides Rating: Least Toxic" at Beyond Pesticides (, "Boric acid ... is a low-toxicity mineral with insecticidal, fungicidal, and herbicidal properties ... however it can still pose health hazards and should be used with care."

According to "Common Cat Toxicities" at Cornell University Department of Animal Science (, "... boric acid ... has a low oral toxicity."

But it is certainly not safe for cats or any animal to eat uncontrolled quantities of it; we were talking about an eyewash. Condolences.


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Ted Mooney, P.E. RET
Pine Beach, New Jersey

March 22, 2012

Hi Ted,

Thanks for your input but the original question was is boric acid safe, so yes, "we" are talking about boric acid in general, "you" were talking about an eye wash :-)

Here's another link which stipulates that extreme care should be taken to ensure that small animals do NOT have any direct contact with the substance:

Better to err on the side of caution, and find a product equally useful, minus the poisoning dangers.

Makes good sense, doesn't it ?

Stacey Gardner
- Catskill, New York, U.S.A.

Hi Stacey. I'm not here to harass a grieving pet owner, but the link you provided suggests that it is important to clean carpets with boric acid, not to avoid doing so.

Mary-Alice was talking about boric acid as an eyewash, and that is the context in which I said it won't kill her cat; I asked Juanita to give us the scenario she had in mind, but she didn't get back to us. There is no such thing as "safe" -- there is only relative safety in various contexts. People have died from drinking too much water, as well as from eating too many hot dogs in a contest.


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Ted Mooney, P.E. RET
Pine Beach, New Jersey

June 21, 2013

Q. I have several feral cats living in my yard. My neighbor has threatened to poison them with boric acid. Will it harm the cats?

Catherine Costello
- Gwymn Oak, Maryland, USA

June 24, 2013

A. Hi Catherine. Yes, certainly it will harm them. If the poisoning is done effectively it may kill them.


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Ted Mooney, P.E. RET
Pine Beach, New Jersey
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