Boric acid is a highly effective method for killing roaches when applied correctly. When a cockroach walks through boric acid, the powder adheres to its body and legs. The roach then ingests the boric acid while grooming itself, which affects its nervous and digestive systems, eventually causing it to die. Boric acid can also be applied to bait and traps, and when used properly, it can take out a lot of cockroaches. However, excessive or improper use can result in a mess and reduced effectiveness. To use boric acid, homeowners must track the pests’ activity to find the right spots to lay down a layer of dust. Correct application is key, and homeowners should avoid spreading boric acid on countertops or any food prep surface. While it’s not usually lethal for adults, consuming this substance or getting it in the eyes causes irritation. Boric acid is considered a relatively safe method for killing cockroaches, but it is important to apply it sparingly and limit exposure to it.