This article is from the Fleas, Ticks, and Your Pet FAQ, by firstname.lastname@example.org (Cindy Tittle Moore) with numerous contributions by others.
Also known as sodium polyborate, sodium tetraborate, sodium borate.
The chemical is related to boric acid. This is present in a variety of
household products. Sprinkling 20 Mule Team Borax, the kind you use in
laundry (*not* the hand soap Boraxo; the soap added to can be toxic to
your pet) on the carpet and upholstery will dry out the deposited flea
larvae. The procedure is to vacuum the house, sprinkle borax or salt
using a sieve on carpet and upholstery (and under the pillows, under
the furniture); sweep with a broom to settle the borax into the carpet
and then vacuum again. Some people leave it on for a few days before
vacuuming, but this runs the risk of abrading the surface of the
carpet. Don't let your animals eat the stuff. If you use borax, you
may need to adjust for this when cleaning your carpets by using less
soap. The effects of a borax treatment seem to last about a year or
Drawbacks: The chemical borax is abrasive, and 20 Mule Team Borax may
abrade your carpets. In addition, there are documented cases of
long-term low-level exposure to sodium polyborate resulting in
conjunctivitus, weight loss, vomiting, mild diarrhea, skin rash,
convulsions and anemia and other similar allergic reactions in humans.
If you're using borax as flea control, and your pets (or family) are
showing loss of appetite, eye or skin problems, anemia or kidney
problems, you may want to switch to another flea control method and
see if their health improves. Do not apply it to damp carpets as it
can take the color out.
Borax is NOT advisable where you have pets which groom themselves,
e.g., cats and ferrets. They can ingest enough to harm them if the
borax is not settled deeply enough into the carpet (October 1992 of
Dog Fancy). Symptoms of acute poisoning include diarrhea, rapid
prostration and perhaps convulsions [these occurred when borax was
scattered openly for cockroach control].
There are various products that are applied in the same way, such as
PEST-X. Check these types of products to see if they contain borax or
boric acid. If so, the above commentary applies to those products as
well. Otherwise, check the ingredients against the other ingredients
Some people use salt instead of borax. Provided that you do not live
in high humidity areas, this is an alternative. Since salt absorbs
water, salt in carpet in an unairconditioned house in Florida (for
example) would mean a damp carpet -- later rotted or mildewed.
A cheap source of boric acid powder is "Terminator". Available in
hardware stores. A 5lb can of 100% boric acid powder is about $22; a
30lb can $54. Customer service # is 800-242-9966.