除虫菊酯，存在于除虫菊（一种菊科植物）的叶子、茎杆，特别是花中，对昆虫具有很强的毒杀作用。把除虫菊的花收集起来晾干，与木屑、香料等混在一起做成烟熏剂，点燃后，除虫菊酯即可随烟雾散发出来，飞舞的蚊子一旦接触到它，就会被毒杀，这种烟熏剂是优良的天然“蚊香”。

除虫菊酯的杀虫谱比较广，能够杀灭许多卫生和农林害虫，并且无抗药性，对人和其他温血动物的毒性也很小，无残毒污染环境。它的缺点是对光的稳定性差，一遇到阳光的照射就容易分解、失效，所以只适合在室内用于防治蚊、蝇，以及蟑螂等卫生害虫，不宜作为农药在田间进行喷洒使用。

The pyrethrins are a class of organic compounds normally derived from Chrysanthemum cinerariifolium that have potent insecticidal activity by targeting the nervous systems of insects. Pyrethrin is synthetically made by industrial methods, but it also naturally occurs in chrysanthemum flowers, thus is often considered an organic insecticide, or at least when is not combined with piperonyl butoxide or other synthetic adjuvants. Their insecticidal and insect-repellent properties have been known and used for thousands of years.