There are lots of old wives tales about why and who get bitten and indeed some people tend to be more susceptible to bites than others however mosquitoes and midges are primarily attracted by the carbon dioxide in the breath. It is thought that CO2 can be detected at 200m away. The combination of CO2 and body smells is most attractive but if you wear dark clothing and move around you may become a prime target for a tasty mea! Once the CO2 is detected the mosquitoes zig zag towards the body heat and then probe and taste the skin and decide whether they want a feast or not.
Repellents help to protect you by masking the smell of the body so that the insects cannot find you as easily. If the smell does not deter, then the taste of the repellent also works to prevent bites. There are various forms of repellents such as roll-ons, sprays, gels, wipes. Repellents should be re-applied regularly especially in hot conditions when they may disappear with sweat or after swimming. They should be applied over sunscreen.