Using a pilot system we have categorised this review as: “Current question – no update intended: further research unlikely to change conclusions" (see published notes).

Malaria is a major health problem that particularly affects people living in sub-Saharan Africa and other tropical parts of the world. It often causes considerable morbidity and mortality especially in children under five. It is transmitted by mosquito bites from infected female mosquitoes. Several strategies and approaches are available for preventing mosquito bites and malaria infection, including repellents, and these approaches will be considered by those living in affected areas and by travellers to areas where there is high risk of infection. Electronic mosquito repellents (EMRs) are designed to repel female mosquitoes by emitting high-pitched sounds almost inaudible to the human ear. EMRs are claimed by their manufacturers to be effective in repelling mosquitoes and preventing disease. No randomized controlled trials were found, but 10 field studies looking at the number of mosquitoes caught on the bare body parts of humans were assessed. These studies were conducted in various parts of the world with different species of mosquitoes and were controlled for factors such as locality and timing. One study used just one observer with seven observations, while the highest assessment included 18 observers with 324 observations. There was no evidence in the field studies to support any repelling effects of EMRs, hence no evidence to support their promotion or use. Future randomized controlled trials are not proposed as there was no suggestion in the field studies that EMRs show any promise as a preventive measure against malaria.