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Compounds and Cleaning · Compound · Antiseptic and insecticide

Boric Acid

A mild antiseptic and a potent insecticide. Used in eye and foot washes and in roach and ant powders.

INDEFINITEMULTI-USEHazardousWorks without power

Quick facts

Chemistry
Weak acid
Form
White powder
Hazard class
Toxic if eaten
Shelf life
Indefinite
Storage
Sealed glass or plastic
What to avoid
  • Moisture
  • kids
  • pets

See everything boric acid must never touch

What it's good for

Roach & ant powder

Potent insect killer

Eye & foot wash

Mild antiseptic rinse

Antifungal

Treats foot fungus

Caution

Keep from kids and pets

A weak acid, mildly antiseptic to people but a slow poison to insects, which swallow the dust as they clean it off their bodies.

Good to know

Boric acid, boron, and borax. Boron is the underlying element doing the work; boric acid is one of its refined compounds, a weak acid, while borax (Chapter 15) is the raw alkaline mineral it is made from. Both owe their punch to that boron atom. An insect walks through the powder, then swallows it while cleaning its legs and body, and over the next few days the boron wrecks its gut from the inside. That slow timing is the trick: a roach can carry the dust back to the nest before it dies. To people boric acid is only mildly toxic, gentle enough that a dilute solution has long served as an eyewash, but keep it from children and pets.

Handling and safety

Toxic if eaten

Effective on insects but harmful to people and pets; place it out of reach.

Patient pest control

It kills roaches and ants over days as they track it to the nest.

Mild antiseptic

Diluted, it serves as a gentle eye and foot wash.

Dust thin, not thick

Insects walk through a light dusting; thick piles get avoided.

Eight jobs it does

  • Insecticide for roaches and ants
  • Antiseptic for minor cuts
  • Antifungal for foot and jock itch
  • Plant fungicide and mildew
  • Wood preservative against rot
  • Fire retardant for insulation
  • Mold killer for damp wood
  • Eyewash (sterile solution only)

If it goes bad Clumps when wet but stays effective once dried out.

What I buy

My pick: boric acid on Amazon.

Recipes for boric acid

Questions this answers

Tap a question for the short answer.

What is boric acid used for?

Boric acid is a potent roach and ant powder and a mild antiseptic. Its jobs include insecticide, antiseptic for minor cuts, antifungal for foot and jock itch, plant fungicide, wood preservative, fire retardant for insulation, mold killer for damp wood, and eyewash as a sterile solution only.

How long does boric acid last in storage?

Boric acid has an indefinite shelf life. If it gets wet it clumps, but it stays effective once dried out. Moisture is the main thing to keep away from it in storage.

How do I store boric acid?

Store boric acid in sealed glass or plastic, away from moisture, and out of reach of kids and pets because it is toxic if eaten. If it does get damp it clumps, but it still works once dried out.

Keep going

Read nextBoraxA naturally occurring mineral salt used for cleaning, laundry, ant and roach baits, mold control, and metal-working flux.Compounds and Cleaning · Compound

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Compounds and Cleaning · Formula Insect Killing Powder for Indoor Pest Control A roach picks up boric acid's fine dust as it crosses a treated crack, then swallows the powder while grooming itself, and the boron goes to work as a slow stomach poison from the inside. Hazardous Compounds and Cleaning · Formula Ant and Roach Bait Using Borax A slow-acting colony killer that foragers carry back to the nest before they die. Handle with care Compounds and Cleaning · Compound Vinegar Shelf life: Indefinite. Storage: Sealed glass or HDPE. INDEFINITEMULTI-USE Garden and Livestock · Formula Baking soda ant barrier and cockroach bait Two uses of baking soda for insects: a dry line to disrupt ant trails and a 1 to 1 sugar or flour bait for cockroaches.
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Compounds and Cleaning · CompoundSource: Prepper's Chemical Survival Guide, Chapter 23, p. 126 · Last reviewed 2026-09-18

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