What is Inside Mosquito Repellent Mats and Coils?

To repel mosquitoes at night, square tablets called "mats" or incense coils are widely available. The mat is placed on a device that keeps it warm using a mild electric current, while the coil is simply lit. Both release a very low-toxicity smoke that kills mosquitoes.

• The Key Ingredient: A white flower called the 'Painted Lady' contains a mildly toxic substance named Pyrethrin. This toxic substance naturally protects the flower from insects.

• How It Works: Pyrethrin is extracted from this flower and mixed into the mats in very small quantities. When the mat is heated by the electric current, it releases pyrethrin smoke. This smoke is enough to kill mosquitoes, but it does not affect larger insects or humans.

• History: In ancient times, people in Iran used the juice of this flower to make oil to kill head lice. Ancient mosquito coils mixed with pyrethrin were also made in China and Japan.