Roaches are prolific breeders known to produce several thousand offspring a year. They thrive in dark and damp places, and their favorite in-home living and breeding grounds are under sinks and refrigerators. Roaches usually come out at night. There are many ways to get rid of roaches, but boric acid is the only natural remedy known. If used correctly, boric acid is one of the most effective cockroach control agents available. Although boric acid is non-toxic to humans, it's highly toxic to roaches. Roaches die shortly after ingesting boric acid. [source: UKAG]

Here is how to use boric acid:

  1. Empty the kitchen cabinets and the area under the sink.
  2. Clean the sink, oven and all cabinets, drawers and countertops with water and a mild detergent.
  3. Clean behind and under the refrigerator. Remove and clean the pan that collects the defrost water under the refrigerator.
  4. Fill any holes or crevices in the walls with a foam filler or caulk. Don't use glue products -- roaches eat glue.
  5. Spread the boric acid all over the kitchen cabinets, drawers, countertops and sink. Make sure you apply it under the sink, oven, refrigerator and dishwasher. Be careful not to inhale the boric acid when applying it. For best results, apply the boric acid at night (when the roaches come out) and leave it until morning. If your house is infested with a lot of roaches, a heavy application may be necessary and you may consider staying out of the house for two to three days.
  6. Vacuum up any remaining boric acid and clean all the areas where the powder was applied with a wet rag, the next morning. You should be rid of the roaches.