It is thought that they are attracted by carbon dioxide emissions, and particularly the smell of sweat, although it is possible that they react to body heat as well. The reason why some people are particularly prone to attack is connected with their individual body smell.
Most mosquito repellents evaporate on the skin and work by blocking a mosquito’s sense of smell, preventing it from finding its target. This is how substances such as icaridine or diethyltoluamide (DEET for short) work. However, while DEET is the most reliable insect repellent available at present – it remains active for up to four hours after it has been applied – it is not considered to be entirely safe, especially in high concentrations. Natural essential oils such as citronella or tea-tree oil seem to cause fewer health problems, but they are less reliable. The only absolutely safe protection is a physical barrier, such as flyscreens on windows, mosquito nets over beds or appropriate protective clothing.