PBO was developed in the late 1930s and early 1940s to enhance the performance of the naturally derived insecticide pyrethrum. Pyrethrum is and was an important insecticide against mosquitoes and other disease-carrying vectors, thereby providing public health benefits, e.g., preventing malaria. Although exhibiting little intrinsic insecticidal activity of its own, PBO increases the effectiveness of pyrethrins, thus is called a synergist.