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Toxic effects of boric acid on animals from ants to feral cats

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 [on eBay or Amazon (adv.)] at the right concentration can be safely used to clean animals' eyes, much 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) were to gobble some 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 for much progress on it :-)

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

A. Home made boric acid roach killer [on eBay or Amazon (adv.)] 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 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 drippings 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 or other enticed boric acid :-(


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

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. update Nov. 2023: That link is for sale; don't go there because it might become a malware site :-(
But the page was captured by the wonderful Wayback Engine of and the article can be viewed here.

We thank Nicholas for demonstrating a good way to provide internet links: with a brief summary, so that when it breaks the response retains value, and people know what they're looking for if they want to try to re-find it. Thanks!

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
CTO - Jackson, Michigan, USA
Plating Systems & Technologies, Inc.
supporting advertiser
plating systems & technologies banner ad
November 17, 2017

Boric acid as eyewash for cats?

Q. Hello,
Most recently my calico kitten has contracted 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

"Cat Owner's Home Veterinary Handbook"

on AbeBooks

or eBay

or Amazon

(affil links)

"The Dose
Makes the poison"

by Frank & Ottoboni
on AbeBooks

or eBay or


(affil links)

A. Hi, Mari-Alice. Boric acid has been used as eyewash for people for many decades, but animals aren't people, and what's good or bad for us might not be equally so for cats. So it may or may not be the best treatment for her eyes, but a boric acid eye treatment won't kill her.


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

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
July 28, 2008

thumbs up sign Indeed, Vera ... thanks.
Although eyewash [on eBay or Amazon (adv.)] and many eyedrops are largely boric acid, such products are pure enough, dissolved surely enough, and at the right concentration to be a better idea.
Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

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 13, 2017

Can boric acid kill a cat?

thumbs down signYes, 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 person 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 20, 2012

Hi Stacey. Very sorry about your cat! Condolences :-(

But that page of "actual scientific info" starts off 100% dead wrong, ludicrously saying: "What Is Borax? Borax is also known as boric acid." :-)
It most assuredly isn't! Borax is Na2B4O7.10H2O; boric acid is H3BO3. That worthless ehow page is beyond ridiculous; "scientific data" is the very last thing it is :-)

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 answering Mari-Alice question about using boric acid as an eyewash, not eating it. Again, sorry for your loss.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
March 21, 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.
March 22, 2012

Hi Stacey. I'm certainly not here to harass a grieving pet owner, and if you can name a product that is equally useful and less toxic, great, 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 person who keeps saying that Boric acid won't kill a cat". Yes, when a thread wanders it is easy for people to misunderstand each other :-(
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. Hopefully readers will piece together safe strategies.

Be well,

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

Boric acid and poisoning of feral cats

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 21, 2013

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


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

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 (e.g., "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 (e.g., "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. (e.g., "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
May 28, 2015

thumbs up sign We don't know Catherine nor her neighbor, but we do know that Catherine in actively encouraging feral cats, which some people consider an actual danger to their children (and destroyers of small wildlife) -- so there may be two sides here. The neighbor may have no actual intention of harming anything, but simply be trying to discourage Catherine's hobby from expanding because, as an animal lover himself, he's unhappy about what she is promoting.

Civil conversation is great, and the right answer! ... but feigning civility to engage in secret recordings, carefully faking it to try to entrap your neighbors into felony convictions? Geez!!

Love of animals is a good thing. But please let's not let "love of animals" be the last refuge of a misanthrope :-)


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

A. 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 C.
- corpus christi Texas
August 8, 2016

thumbs up sign Thanks Ted. There is benefit to calm discussion and seeing the other's person point of view.

In my wall-to-wall suburbs there hasn't been a snake, raptor, bobcat, weasel, owl, fox, coyote, wolf, or other hunter for at least 75 years. This total elimination of carnivores means that the swarms of chipmunks, squirrels, geese, rabbits, deer, groundhogs and other herbivores in every 100 x 100 lot totally strip bare every vegetable patch & flower garden in spring, then the animals succumb to starvation & disease (we pick up several dead chipmunks and rabbits every fall) ... that isn't the natural ecological order either.

I don't want a pack of feral cats in my backyard, but I'm always happy to see an occasional neighborhood cat passing through the yard as a counterbalance to my completely unnatural suburb, and its ridiculous concentration of chipmunks, rabbits, and squirrels :-)

I certainly agree that people should concentrate on helping their neighbors, rather than trying to trick them into felony convictions :-)


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

thumbs up sign Thanks Ted C. for your opinion as an Environmentalist. I would disagree that feral cats are useless. Living on a farm, you need to have domestic & feral cats -- we called them "mousers" -- to eradicate mice, rats, rabbits & other small critters from destroying your garden, animal feed, hay & invading your home. Not to mention the hantavirus that is carried by mice & rats. I have heard stories from neighbors & have seen feral cats scare off deer, which will eat your garden, coyotes that want to dine on your chickens, & even dogs that love to dig up whatever you put in the ground. This is applicable to urban areas too.
In Az we have an issue with scorpions which are nearly impossible to eradicate. Any exterminator will tell you the best way to get rid of scorpions is to have a cat, both inside & outside your home. It's not that cats are immune to a scorpions venom, it's their fur & skin that wards off the scorpions stinger.
My last point is a religious one. God didn't create anything to be "useless". Every living creature, be it human, animal or insect, has a purpose, even cockroaches. Roaches clean the environment by feeding on decaying organic matter, leaf litter & wood around it. In the process the roaches body traps a lot of atmospheric nitrogen. (Info on roaches from a popular exterminating company.) As an Environmentalist, sure you understand, don't mess with "Mother Nature". Be blessed!

Kathy M.
Retired RN - Phoenix, Arizona
January 3, 2022

"You are a child of the universe. Just as much as the stars and the trees you have a right to be here" -- The Desiderata

thumbs down sign To Ted, "the environmentalist".

When they got rid of feral cats, the black plague ensued and killed quite a few people. So please "Mr. Environmentalist", educate yourself and keep your mouth in check, as we don't want history repeating itself.

It is not in any way kind or good for the environment to kill feral cats. They've actually done quite a few studies on feral cats and the bird population. Given that most birds can fly, the birds that cats do manage to catch and kill (which are relatively few), are birds that are weaker, and by body weight have less muscle tone than healthier birds; these birds would have died anyways.

Birds can fly and easily escape a cat. I see it all the time. A cat also won't take on a bigger bird as they have sharp beaks and can hurt a cat. Once in a great while, a cat manages to catch a bird, but they are not lowering the bird populations around the world. That is more effectively being done by GMO corn, pesticides, climate change and all kinds of other things.

Birds also carry a variety of diseases, like the bird flu, which can affect humans (cats don't carry transferrable diseases). Many birds nest in attics and damage roofs and exteriors of homes. The bird population also very much needs to be kept in check.

Please stop promoting the idea that feral cats, who are born without a home by no fault of their own, deserve to die.

Everyone should encourage others to TNR feral cats. That is what is kind and will keep the population in your area in check. There are local groups in every area that will assist with trap, neuter & return (TNR).

And it's people like you, Ted the "environmentalist", who strangely them call themselves environmentalists but have no clue that cats are a very important part of the ecosystem, that need to be called out for your incorrect and ridiculous assertions.

Nica S.
Cat appreciator - Austin TX
November 7, 2023

thumbs down sign Hi Nica. You make some good points and are certainly welcome to present them here :-)

But this isn't Facebook and its toxicity, this is my site where I've invested 34 years of my life trying to build a community of camaraderie & aloha -- and snideness isn't welcome.

Express your opinion, but please try to "keep your mouth in check" rather than expressing scorn for others. Thanks!

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

Also, I took in a "feral" cat that was shot by someone in Corpus Christi, TX, where Ted C. is from. That cat can't walk now. He is a great, adorable friendly cat and definitely didn't deserve that fate. My husband and I have spent a lot of time and money trying to help this cat, including removing the bullets from him, as he very undeservedly was shot, likely by someone like Ted C., who falsely thinks feral cats are killing his precious birds. In TX, it is unfortunately not against the law to shoot animals, although it should be, like it is in NY, where I'm originally from.

These false statements that cats are causing bird populations to go down really need to be stopped. This idea causes severe and unreasonable reactions by people like Ted C., who strangely believe they're being environmentalists by promoting the idea of killing feral cats (and others like him who then go about actively attempting to kill them). Cats and birds have lived together for centuries. The bird issue is not due to cats.

So though at the same time that I understand you feel my comment was "toxic", I just want to point out that if you do allow people to post things on your site that actively encourage the killing of animals on your site, that in itself is not very peaceful, non-toxic or aloha. And you have to expect that Ted C.'s comment is going to cause a passionate reaction by some.

So again, sorry if I disrupted your site with what you see as a toxic attitude, but I actually think it's Ted C. who deserved the type of response you gave me.

Thanks again & take care.

Nica S.
- Austin TX
November 14, 2023

A. Hi again. The problem this site has is not your opinion about feral cats which, again, is *absolutely welcome*, but your disdain for those who think otherwise and who suggest "humanely as possible" elimination of what they consider dangerous pests. Euthanasia is often suggested as a humane solution for people, let alone feral packs of dogs & cats.

We've now been forced to remove Ted C.'s last name because another woman, whose posting we're not going to run, and perhaps motivated by a notification from you wrote:
"[he] came here to find an additional way to kill feral cats and encourage others" ..."those who kill cats often go on to kill people" ... "who actively encourages the death of animals is not psychologically sound".

I consider it absolutely outrageous for anyone to imply that someone they don't know is "not psychologically sound" and might "often go on to kill people", just because they don't share their opinion on feral cats. I know which person I think is "not psychologically sound"! I won't be patronizing her restaurant but I won't be posting her diatribe either.

Although Ted C. had his say, so did feral cat lovers Catherine C. & Jackie P. & Kathy M., and now you've had yours. This thread is struggling to return to its mission of discussing the beneficial uses and possible hazards of boric acid rather than being ground zero for a feral cat debate. Meanwhile an adjacent town just passed a new law that it is illegal to encourage homeless feral cats by feeding them :-)
Best Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

Boric acid as ant poison

thumbs up signI just used a mixture of borax [on eBay or Amazon (adv.)] (laundry soap), sugar and hot water in a 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
May 30, 2015

A. Hi Charles. I personally try to discourage ants from my house, but don't see any problems with ants outside -- but your situation may be different.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

Borax powder for arthritis?

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
October 27, 2017

Ed. note: We don't believe in censoring people's opinions nor their anecdotes; but that certainly doesn't mean that the editors believe that this action was safe or effective :-)

Rabbit might have eaten roach killing tablet

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

Toni Bruder
Buyer - Islip new york
September 27, 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. But if there's just a tablet missing without a good explanation, I personally wouldn't -- there's about 145 tablets in 6 oz., and they're only 40% boric acid, so it's not much boric acid ... but if it was my grandchild rather than my rabbit I probably would :-)


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

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