Boric Acid & Spiders

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Spiders dont like boric acid.

Boric acid, while harmless to humans, is toxic to spiders. Boric acid is made from boron, which is a substance that is found commonly in nature in soil and water. Boric acid is harmful and abrasive to the outside of the spider, and when the spider eats this substance, it will die.


Boric acid has been known to be toxic to spiders and insects for many years. Boric acid and its salts have been used in pesticides and insecticides since 1948 in the United States.

Reasons to Use It

Boric acid is a better alternative than using chemicals that could be toxic to humans or their pets. This is a natural and non-toxic way to keep spiders out of the home or to exterminate them once they have made a spot in your home. It is also environmentally friendly because you will not be releasing toxic chemicals.

How to Use Boric Acid

For some reason there are a number of people who find spiders to be undesirable to have around their home. Most spiders are not toxic to humans and they help to keep the insect population down. A good way to keep spiders out of the home is to put boric acid in any cracks or fissures along walls, doors, windows, fixtures, cabinets and baseboards that you might have. Additionally, place the boric acid behind and under any appliances, around pipes and drains and cabinet drawer wells.

How It Works

If the boric acid does not deter the spider from coming in through any of the cracks or openings it is placed on, it will eventually work by killing the spider. The boric acid is caustic to the outside of the spider but it becomes fatal once the spider ingests it. The spider will ingest the boric acid once it grooms itself.


Spiders serve a purpose in the ecosystem, and while you might not be eager to have them in your home, they will give it the same benefit. Spiders can help keep your home free of other insects that you might want around even less than spiders. Keep this in mind before you go overboard with the boric acid and kill every spider in sight.


Marie Scribe

Marie Scribe has been writing for more than 10 years. Her specialties include copywriting, advertising and editing. She has a journalism degree and extensive experience with business and technical writing. She has been published on and eHow.