Catnip May Be the Purrrfect Safe Insecticide

Close up of tabby cat hiding in a clump of blooming catnip plants

We know cats like catnip. Now we learn insects do not.

The active component of catnip (Nepeta cataria) repels insects by triggering a chemical receptor that spurs sensations such as pain or itch, researchers reported in Current Biology.

The sensor, dubbed TRPA1, is common in animals — from flatworms to people — and responds to environmental irritants such as cold, heat, wasabi and tear gas. When irritants come into contact with TRPA1, the reaction can make an insect flee.   

Catnip’s repellent effect on insects — and its euphoric effect on felines — has been documented for millennia. Studies have shown that catnip may be as effective as the widely used synthetic repellent DEET.

Researchers discovered all this by exposing mosquitoes and fruit flies to catnip and monitoring the insects’ behavior. Fruit flies were less likely to lay eggs on the side of a petri dish that was treated with catnip or its active component, nepetalactone.

Mosquitoes were also less likely to take blood from a human hand coated with catnip. Insects that had been genetically modified to lack TRPA1, however, had no aversion to the plant. That behavior — coupled with experiments in lab-grown cells that show catnip activates TRPA1 — suggests that insect TRPA1 senses catnip as an irritant.

Puzzling out how the plant deters insects could help researchers design potent repellents that may be easier to obtain in developing countries hit hard by mosquito-borne diseases.

If a plant can make a chemical that activates TRPA1 in a variety of animals, none are going to eat it, according to Paul Garrity, a neuroscientist at Brandeis University in Waltham, Massachusetts, who was not involved in the work. 

But now this research has scientists scratching their heads about catnip’s relationship with cats. The question is not only whether catnip targets TRPA1 in cats but also whether the plant might send signals through different cells — such as those for pleasure — in the feline nervous system.

Luckily, the plant’s bug-off nature doesn’t affect people — a sign of a good repellent.

In fact, catnip is an important aromatic medicinal plant for humans that contains antioxidants and volatile compounds like nepetalactone, thymol, and pinene that may have medicinal benefits.

Catnip may help relax the body before bed and promote rest. Its calming properties come from its nepetalactone and nepetalactone acid compounds.