Reader Question Erison Siqueira, Sao Paulo, SP
Illustrates Maíra Valentim
Edition Felipe van Deursen
Made in China
The device is a resistor, capable of transforming electrical energy into heat. The heat, in turn, causes the evaporation of a chemical compound that is toxic to insects called a pyrethroid. Launched in 1980, the product is a synthetic equivalent of pyrethrin, repellent present in the chrysanthemum and known for at least 2,500 years. The Chinese already used the powder of dried flowers to ward off insects.
How to use
Although effective in repelling any insect, manufacturers recommend that the repellent be used especially against mosquitoes, such as aedes aegypti, transmitter of dengue and zika. It works in areas of up to 10 m². For larger locations, it is recommended to use more than one repellent. The environment must have an air current to dissipate the product, which must not be placed behind furniture or above the height of the bed.
crazy mosquito
The pyrethroid penetrates the insect’s organism through respiratory holes, the spiracles. It reaches the nervous system, where the action of the repellent start. Intoxication has four levels: excitement, convulsion, paralysis and death. If it fails to flee before becoming completely paralyzed, the insect dies.
- Repellents and insecticides generate resistance in insects. That is, over time, they can become immune
- O repellent electric is not recommended for those with breathing problems. He must be at least 2 m from the bed
prize lie
Repellent electronic is controversial
Another product found on the market is the electronic repellent – there is even a mobile application version. Its supposed active principle is the emission of ultrasonic sounds, imperceptible to our ears, which imitate the flapping of wings of natural mosquito predators. The problem is that its effectiveness has not been scientifically proven. In the summer of 2012, Band FM in São Paulo broadcast a high-frequency signal (15 kHz) that supposedly simulated the flapping of a dragonfly’s wings, a mosquito predator. The campaign, created by the Talent agency, won an award at the prestigious Cannes Festival, but was criticized by biologists and entomologists, who considered it irresponsible and a lie.
CONSULTANCY Ademir Martins, biologist and entomologist, researcher at the Oswaldo Cruz Institute
SOURCES Faculty of Pharmaceutical Sciences of the State University of São Paulo (Unesp), National Pesticide Information Center, University of New Mexico (USA), National Institute of Health (USA)