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topic 11228

Toxic effect of boric acid on animals

A discussion started in 2001 but continuing through 2019


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

Juanita Oakes
- Little Rock, Arkansas

affil. link
Boric Acid Powder


A. Hi, Juanita. I would guess that boric acid at the right concentration can be safely used to clean animals' eyes as it is used on human eyes. But if an animal (a rat you are trying to poison? or a pet you are trying to keep safe?) gobbled it down, and whether they would do so, I don't know.

Please try to give us the scenario you envision. Your question is too open and abstract. Thanks!

Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha


A. Home made Boric Acid Roach Killer 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


thumbs up signThanks James, now I see. Yes, boric acid is blended with attractive foods like sugar to get ants to eat it and be poisoned. I can also imagine a scenario where a dog might have no interest in eating plain boric acid but might chow down on sweet ant traps :-(


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha


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 demonstrating a good way to provide an internet link: with a brief summary of what it says, so that when it breaks (which they usually do rather 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

affil. link
"Cat Owner's Home Veterinary Handbook"
from Abe Books


affil. link
"The Dose Makes the Poison"
from Abe Books


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.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

July 28, 2008

A. Use regular eye drops on your kitten. It's much safer and it cleared up my son's kitten overnight.

Vera L Taylor
- Taylor, Florida

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. Very sorry about your cat! Condolences.

But that 'actual scientific info' page starts off 100% dead wrong with "What Is Borax? Borax is also known as boric acid." :-)

Borax is Na2B4O7.10H2O, boric acid is H3BO3. That ehow page is completely ridiculous, and the very last thing in the world it is is "scientific data" :-)

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; James said he had pets who survived it but were sick from it, and I was talking about boric acid an eyewash. Sorry for your loss.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

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 [returning]
- Catskill, New York, U.S.A.

Hi Stacey. I'm certainly 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; to which you responded "Forget the misinformed persons who keeps saying that Boric acid won't kill a 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 specific contexts. People have died from drinking too much water, as well as from eating too many hot dogs.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

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 C [last name deleted for privacy by Editor]
- Gwymn Oak, Maryland, USA

June 24, 2013

A. Hi Catherine. Yes, certainly it would harm them. If the poisoning was done effectively it might even kill them.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

May 28, 2015

A. Your post is from 2013. I hope your cats have remained safe.

In NEW YORK, poisoning these cats would be considered animal abuse - and is considered a Felony, punishable by jail time. I don't know if this is true in your state. Try to find out.

IF SO - and IF YOU RECEIVE MORE THREATS from this neighbor: 1.Report it to the police.
Having proof with you is best - so keep a hidden recorder with you - and converse in a polite, CIVIL manner with this neighbor about this issue. Try to get them to talk about their threats (eg. "Do you really intend to poison the poor cats?")
[Smart phones generally will record very well, and can be kept in a shirt pocket, or, maybe even in your hand. You can also buy inexpensive computer USB's ($10-20) that ALSO record on their own. Check or Amazon.
You might also consider leaving a note with your neighbor asking them not to harm these cats with poison or any other means. (You can use a personal reason (eg. "I Love them", and/or, "they are not causing you any harm"). Because, if you're lucky - they MAY respond to your note with a note threatening the cats again (Or confirming previous threats)- another form of proof. (Don't tell them it's illegal yet - or you may not get the response you want!)
2. If all else fails - can you bring these cats into your home?
There are many animal rescuers who are adept at trapping. Look on internet for cat rescuers nearby. Are the cats friendly/handlable by you - or are they Feral (Not handleable)? (I've taken several Ferals into my home. Still can't touch them, but they're wonderful!) Have them taken directly to a vet first - to have them tested for Leukemia/AIDS - with a vet who confirms he/she can handle ferals if they're feral. (Some rescuers can do this testing for you inexpensively - Ask). AIDS-Positive cats can be kept safely with Normal Cats - as long as there are no REAL FIGHTERS. Sharing Food/Water, and even "Play" bites will not transfer the disease. Only DEEP bites are risky.). Leukemia-Positive cats must be kept in separate rooms from AIDS or Normal cats. Leukemia transfers very easily.

If, sadly, the cats were already killed - again, you can try to engage your neighbor in a polite, CIVIL conversation about the happening - and record it. (eg. "How could you have the heart to kill these cats?") (Or, again, by note.) If this is a felony in your state - the statute of limitations may not have run out yet for prosecuting them - if you have proof.
Good Luck, Jackie

Jackie P [last name deleted for privacy by Editor]
- New York, New York, USA

June 2015

thumbs up signHi. Civil conversation is great, but feigning civility to engage in secret recordings not so much (and illegal in some states). To suggest that she not tell him poisoning is illegal in order to trap him in a felony?

We don't know Catherine nor her neighbor, but we do know that Catherine in actively encouraging feral cats, which some people consider to be terrible destroyers of small wildlife -- so there may be two sides here; the neighbor may have no intention of harming anything, but is simply trying to discourage Catherine's hobby from expanding because, as an animal lover himself, he's sickened by the carnage she is promoting.

Love of animals is good. But let's not let a "love of animals" be the last refuge of a misanthrope.


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Aloha -- an idea worth spreading

August 8, 2016

If you have feral cats living in your back yard, the best thing you can do it exterminate them as quickly and humanely as possible.

Feral cats are a bane to the environment and the ecology.
They decimate the indigenous small animal/bird population and provide no useful contribution in return.
They have a negative effect on the entire ecosystem and disrupt the natural food-chain.

As an avid environmentalist, I see this regularly.

... Find something more useful for your emotions, like maybe helping people instead of animals?
Just saying

Ted Clinton
- corpus cristy Texas

August 2016

Thanks Ted.

But in my wall-to-wall suburbs there hasn't been a snake, raptor, bobcat, owl, fox, coyote, or hunter for at least 60 years. This complete lack of natural enemies to the swarms of chipmunks, squirrels, geese, rabbits, and groundhogs in every 100 x 100 lot, means that every vegetable patch & flower garden is stripped totally bare, then the animals succumb to starvation and disease -- so this isn't the natural ecological order either. I agree that I don't want a pack of feral cats, but I'm always very happy to see an occasional neighborhood cat passing through as a tiny counterbalance to my wholly unnatural suburbs and it's unnatural concentration of rodents and other pests :-)

But I certainly agree that people should concentrate on helping their neighbors rather than trying to trick them into being charged with a crime :-)


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Aloha -- an idea worth spreading

May 30, 2015

thumbs up signI just used a mixture of borax,(laundry soap), sugar and hot water in container with holes in the lid, I tipped it over and some ran out on the lawn. I've been researching and of course, you should never let your animal eat anything off the ground, but the amount in the container would have to be fully ingested by a cat or dog to be toxic, and death is not the reaction that would ensue. 5 tbsp of borax and 5 tbls of sugar and 1/2 cup of warm water in a container with holes turned over so ants can take it to the queen. I have a service dog, and, although I won't let him roll in it or lick it, I'm not too concerned about toxicity.

charles brink
- Greenfield, Massachusetts usa

October 27, 2017

In regard to the ingestion of Borax, here is a story. I was telling a friend that 1 tsp of borax powder in a litre (quart) of water will dissolve, and taking 3 tsp of the resulting liquid over the period of a day, for 3 months has been known to cure arthritis in people (google it for your own pleasure)
He, with arthritis, wanted to give it a try ... but googled it later and saw someone mentioning 1 tsp of powder under the tongue, which was NOT what I had talked about. Anyway, he later found the mixture I had suggested but it was too late. He had put the 1 tsp of powder under his tongue.

Well, he came to my place two days later very excited. His doctor had told him that he probably had a hardening of the muscles in his throat, and that was the reason he had been having a lot of trouble swallowing for the past 2 years. But after the borax under the tongue he could swallow quite well the next day, and on the second day did not notice any problems at all, and the pain associated with swallowing was gone.
End of story.

raelph houghton
retired - Sunshine coast, qld., Australia

Ed. note: We don't censor people or the anecdotes they post; that doesn't mean that the editors necessarily believe that the action was safe or effective :-)

November 13, 2017

My grandmother put a pinch of boric acid in water and boiled it for a minute to make an eye wash cure for pink eye.

Melissa Koski
- COLUMBIA South Carolina USA

November 17, 2017

silly :-)  Gotta love the Euros! They put boric acid and borax on their SVHC lists. They consider boron compounds substances of very high concern,

Tom Rochester
Plating Systems & Technologies, Inc.  
supporting advertiser
Jackson, Michigan, USA
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Harris roach killing tablets

September 27, 2019

Q. My house rabbit may have eaten a tablet of Harris famous coach tablets. Will it kill him ?

Toni Bruder
Buyer - Islip new york

September 2019

A. Hi Toni. Unfortunately you don't know whether he did or he didn't and therefore whether it justifies the hassle and cost of a trip to the vet. That's more a question of likelihood and personal philosophy than anything else :-(

If your pet gets sick or dies you'll be unhappy, but if you waste money on the vet you'll be unhappy. All I can say is if you're quite sure he did, you should probably take him. If there's just a tablet missing without a good explanation, I personally wouldn't, but I can't criticize someone who would because if it was my grandchild rather than my rabbit I certainly would :-)


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Aloha -- an idea worth spreading

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