What Is the Ratio of Borax & Salt for Killing Fleas?

Written by erin ringwald
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What Is the Ratio of Borax & Salt for Killing Fleas?
Mix salt with borax to kill fleas. (Hemera Technologies/PhotoObjects.net/Getty Images)

Once one or two fleas find their way into your home on the back of the family pet or by hitching a ride on your pant leg, you can quickly have a full-fledged infestation with thousands of fleas. Many commercial and home remedies exist to fight a flea infestation. These remedies vary in price and effectiveness. One option is a mixture of borax and salt.


When choosing a flea treatment, if you have pets or children in the home, finding a treatment that is free of toxic chemicals is important. Borax and salt mixtures fulfil this need. Made from a naturally occurring mineral known as either boric acid or sodium borate, borax is a fine powder used in many cleaning supplies. Uses of the powder include antiseptics, enamels, fertilisers and cleaning agents. It also functions as a preservative when used in small doses. You can find borax in the cleaning supply aisle at your local grocery store. Borax works to dehydrate the fleas, resulting in their death.


Salt has a similar effect on the fleas that borax has, causing the fleas to dehydrate and die. However, because the grains have sharper, more abrasive edges than borax, it also scratches the outer layer of the fleas, causing quicker dehydration. Use regular table salt for the best results.

Ratio of Ingredients

To create your own borax and salt mixture, mix the two ingredients in equal parts. Pour the mixture into a flour sieve. Turn the sieve's handle to sprinkle the mixture on carpets and any upholstered surface. Lift couch and chair cushions and sprinkle underneath them and under furniture as well. After letting the mixture sit for four to eight hours, vacuum it up. Empty the contents of the vacuum into a sealable bag, and discard it outdoors to prevent fleas from escaping the canister or bag. However, according to Science Daily, most fleas die because of the trauma caused by the vacuum.


Although both salt and borax are safe flea treatment options, some precautions should be followed. If swallowed, especially in large quantities, borax ingestion may cause vomiting, fever or diarrhoea. Skin irritation is another concern. It is possible, in prolonged exposure, for blisters or rashes to occur. To avoid accidental ingestion or prolonged exposure, keep borax out of the reach of children and pets. During application, keep children and pets out of the treated area. For salt, avoid use during humid weather. Salt absorbs moisture, which may lead to mildew and mould on upholstered surfaces. To prevent damage to carpet and upholstery, test the mixture in a small area to make sure it does not damage the surface.

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