Q. Cockroaches are taking over the kitchen in my apartment! My grandmother said she took care of cockroaches by putting out little balls of boric acid mixed with flour, bacon drippings, and chopped onions. Does this work?

A. Please don’t do this! It’s not safe. This idea circulated years ago, originating as a household hint from a newspaper advice columnist, who shall remain nameless.

Because you can buy boric acid powder over-the-counter and because it has various first aid uses, including as an eye wash, people assume it’s completely safe. The boric acid that you buy in the pharmacy is very concentrated, about 99% pure boric acid. When you make an eye wash, the boric acid is greatly diluted with water which makes it safe to use. But when ill-advised people sprinkle boric acid powder straight from the bottle onto their kitchen countertop for ants or roll it into dough balls for cockroach control, they are using the undiluted, pure boric acid.

Bet you’ll be surprised to know that less than two teaspoons of pure boric acid can kill a child. Less than two tablespoons can kill an adult. Add to that the fact that you are mixing it with food products like flour, onion, sugar, and bacon supposedly to make it attractive to cockroaches. Guess what? That also makes the boric acid balls more attractive to children and pets.

Having said all that, let me say that boric acid is an effective and safe control for cockroaches when it is formulated properly by a manufacturer and applied correctly. Boric acid dusts or baits that pest control professionals use are only about 1 to 5% boric acid. Pest control professionals also carefully place the boric acid in cracks and crevices out of the way of children and pets, or in tamper-resistant bait stations. Just one more reason not to believe everything you hear and to leave the use of pesticides to professionals.