Scientists in Iran have found that electronic mosquito repellents which are marketed as being able to drive insects away with high-pitched sounds do not work.
A team led by Dr Ahmadali Enayati, from the Mazandaran University of Medical Sciences in Iran, analyzed 10 studies conducted in North America, Russia and Africa.
All were field-based studies which occurred in a natural setting rather than a laboratory.
Malaria which is contracted from mosquito bites affects more than 250 million people worldwide and results in over a million deaths each year; it is particularly prevalent in sub-Saharan Africa.
No vaccine against malaria is available.
Electronic mosquito repellents (EMRs) are battery-powered hand-held devices that emit a high frequency buzz almost inaudible to the human ear which claim to repel mosquitoes within a range of up to 2.5 metres, both indoors and outdoors.
Mobile phone companies too also market a ring tone that is said to deter mosquitoes.
The devices target female mosquitoes, because they are the ones which bite and are supposed to mimic the flight sound of males; it is thought as they mate only once in their lives, this may repel the female insects once they have mated.
The noise is also said to sound like bats, which prey on mosquitoes.
The ten trials assessed the number of mosquitoes landing on the bodies of human volunteers and the scientists found in all ten there was no difference in the number of mosquitoes found on the bare body parts of the human participants with or without an EMR.