Boric acid although is not harmful on humans and pets, it is very harmful to cockroaches. To use it properly, first you must know the places where the cockroaches frequent. If you use it in a place where they do not move around much, it is of no use. It could be hollow spaces in the cabinet or kitchen shelf or under the stove or refrigerators. Switch off the light for some time and then come back and switch it on to check where they are moving around most. Once you find out the place where they frequent most, dust a very thin layer of boric acid. A common mistake that many do is to put too much boric acid in one place. The cockroach is not going to climb over the hill of boric acid to reach the other side. It is always easier for it to go around it. Hence, it has to be a very thin layer of dusting. When it is thin layer, the cockroach will walk right through it, and the fine dust of boric acid will stick to the cockroach legs, and when they clean their bodies by licking, they will be ingesting the boric acid which will eventually kill them. Since roaches feed on their own dead ones when the others eat this boric acid poisoned roach, they too will die. It will take at least 3-4 weeks to see some result.
Of course, this method of cockroach extermination comes in handy for some time. Ultimately, you will need professional pest control help for a proper cockroach extermination to get rid of them completely. Professionals have the most advanced technologies and methods to free you from pest infestation