Boric Acid

Boric Acid has anti-viral, anti-fungal and anti-bacterial properties; it creates an environment inhospitable for these organisms to survive.  I have found Boric Acid an effective topical agent, but as with all chemical use, dosage and proper handling is key.

I have used Boric Acid myself for many years- I remember my grandmother making an eye-wash at home anytime someone had a sty or conjunctivitis.  I have found many uses for it in my animals as well.  In my research, however, I have found studies linked to problems with sperm and pregnancy, so I wouldn't suggest using it on stud males and Never use anything on a pregnant cat (or human) that isn't specified 100% safe!  All studies indicating danger and toxicity are based on ingestion or inhalation and in large quantities.   I have found no studies that indicate these reproduction issues stemming from absorption, but would use lowest quantities on stud males and only if other cures have failed (such as ear cleaner). 


How toxic is boric acid?

The following table lists the LD50 rating for several common substances as published by the Registry of Toxic Effects of Chemical Substances:


(milligrams of dose/kg of body weight)

The LD50 rating is a dose that would cause the deaths of 50 percent of a specific animal population.
One method used to determine the LD50 rating for most substances is via laboratory-controlled oral doses to rats.

The greater the  LD50 rating is, the safer the substance is; in other words it would take a much higher oral dose to kill.

Based on the data we see in the chart, Boric Acid is more than twice as safe as common Aspirin and only slightly less safe than table salt.



 Boric Acid


 Table Salt


 Boron #10


 Baking Soda


 Grain Alcohol


I am not a vet and do not intend to advise anyone on healthcare for their pets.  Do your own research and make your decisions on what you're comfortable with.

From Wikipedia:

While strictly speaking, Boric Acid is poisonous if taken internally or inhaled, it is generally not considered to be much more toxic than table salt (based on its mammal LD50 rating of 2660mg/kg body mass). The Thirteenth Edition of the Merck Index indicates that the LD50 of boric acid is 5.14 g/kg for oral dosages given to rats, and that 5 to 20 g has produced death in adult humans. The LD50 of sodium chloride is reported to be 3.75 g/kg in rats according to the Merk Index. According to the Dutch Health Council(1998/19) Boric Acid should be regarded as if it impairs fertility in humans (R60).


I have used boric acid as an eye powder and for chin acne in young males who grew to be prolific studs, but that's just my own observation.  While the LD50 chart indicates low quantities ingested do not pose a significant health risk, I take all precautions to prevent ingestion or inhalation no matter the application for which it is being used.


Here are a few recipes for topical therapy:

Eye & Wound Powder


1 Teaspoon Boric Acid powder
1 Tablespoon Corn Starch
1000 mg Amoxicillin powder
    (4 fish-mox capsules opened)
This basic recipe can be used many ways.  You can also forgo the Amoxi for many applications (I am allergic to all cillins, so if I need an eyewash for myself, I don't use that part!)
For minor eye irritations:  With a wet cottonball, dampen the area, then apply a light dusting of the E&W Powder to area.  It's okay if some goes in the eyes!  Treat twice daily until problem is resolved and then an additional two days.  1 Teaspoon of Boric Acid mixed in 4 cups of distilled or boiled water can be used as an eye-wash if you prefer direct liquid application.  When using a water-mix, discard unused portion after 1 week and start a fresh batch.
For Chin Acne, lip flap dermatitis, saliva, urine or eye stains and discoloration on light colored coats:  mix just enough distilled water into the E&W Powder to make a paste.  Using a small stiff brush, work it into the fur down to the skin, saturating all affected area.  Blot excess.  Treat once daily until issue is resolved and then weekly to keep it under control if chronic problem (usually I find once the issue is resolved it stays away). When using a water-mix, discard unused portion after 1 week and start a fresh batch.

Ear Cleaner
shake well before each use


1Tablespoon Boric Acid
1 Tablespoon white vinegar
4 ounces Distilled Water

This is an excellent ear cleaner for prevention of "swimmer's ear" if your animal gets water in the ears from bathing, and it makes a great antiseptic cleaner for minor ear infections and generally waxy ears.

For Humans:

All of the animal treatments are also good for humans!
Some other human health applications:

1 teaspoon Boric Acid mixed with 4 ounces distilled water is an excellent antiseptic/antibiotic for minor scrapes.  It also relieves itch from chiggers, mosquito bites and minor rashes.

Dust clean feet with straight boric acid powder and put on white cotton socks - after 3 days treatment your feet will have practically no odor and will sweat less.  Repeat as necessary, but this treatment supposedly has a cumulative effect and after a few treatments feet should stay dryer and odor free for years.  It also cures Athletes foot and other fungal infections.

Get empty gel-caps from a pharmacy or natural foods store - fill one with boric acid and insert in vagina twice daily to cure yeast infections in 2 days.

Fire Retardant
Boric acid and Boron have been used for centuries to pre-treat clothing to be more fire-retardant.  It is used as a pre-treatment on lumbar and wood surfaces as well.

Insect Killer - many sites describe usage in killing crawling insects including ants, roaches, silverfish, centipedes and wood damaging beetles.  Simply apply straight powder to crevasses, back of cupboards, anywhere that is inviting to creepy-crawlies and NOT accessible to pets or humans.  Enclosed "pellets" can be made with peanut butter or corn-syrup to attract pests and keep the contents safe from accidental ingestion.  Boric Acid works as a desiccant to these pests, wearing away their outer shell and also destroying their internal organs, so they don't develop an immunity to it as they will to chemical insecticides.  It is effective as a flea control as well, though care must be taken to limit exposure:

Simply sprinkle it on the carpet, (same mix as above for silverfish) brush it in so it settles down and in the fibre, let it sit for about a week then vacuum and fleas will be gone, eggs and all!  Personal Note:  I would not use this method in an area where animals live due to the dust they raise walking across the surface and what they may ingest when cleaning themselves.  I would clear the area of all traffic, sprinkle the Boric Acid and then vacuum thoroughly and toss the bag out before allowing the animals back in the area.

An EPA assessment of a boric acid pilot pest control program conducted at the U.S. Army’s Aberdeen Proving Ground in Maryland found that boric acid was both more economical and more effective than a monthly spray treatment. Do to its unique mode of action, insects do not gain resistance to borates. It is water resistant, heat resistant and remains effective for long periods of time. Borates are the most effective treatment for many crawling insects including, cockroaches, silverfish, larder beetles, carpenter ants, and other wood borers, as well as wood decay organisms.

Cleaner and Odor control
To eliminate the mould and musty smell in your dishwasher or de-humidifier, just add a tablespoon of boric acid to the water, let it sit 30 minutes, flush it out and the odor is gone.  Add to detergent to brighten, fight stains and eliminate odors from laundry.  When used for cleaning floors, be sure to rinse thoroughly to avoid ingestion by animals cleaning their feet.  Not recommended for cleaning in food preparation areas.

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