How mosquitoes find us:
Before we can understand how mosquito repellants work, we need to understand how mosquitoes find us in the first place. Unfortunately for us, mosquitoes have evolved 3 ways of seeking out a meal. Each of these methods, used in tandem, enables them to fly in for the bite.
- 33 – 99 feet: At this distance mosquitoes rely on their sense of smell, specifically the CO2 plumes we, or other animals, emit. Experiments have shown that the female mosquito only pays attention to the next cue once the first is present and they are closer to the source.
- 15 – 33 feet: The mosquito has homed in on the scent and at this distance is now searching for visual clues to spot you. They are seeking the source of the CO2, not for a shape or body.
- 1 – 3 feet: The mosquitoes now rely on thermal sensory input to locate heat and moisture sources. This prevents them from wasting time on objects such as a rock or vegetation.
What repellents do:
So how do repellents work? DEET was developed by the military over 50 years ago but it was only more recently that studies have been done to understand exactly what it does. Mosquitoes smell with their antennae, which are covered in olfactory nerves. The nerves are essentially equipped with odor receptors, that bind to odor molecules and trigger neural activity. Simply put, DEET binds to these receptors leaving the mosquito confused and unable to smell you. The DEET over-activates the receptors rendering their ability to smell useless.
According to many studies, the only repellent that comes close to the ability of DEET is lemon eucalyptus oil with the caveat that natural products break down faster and thus must be applied more regularly. It should not be applied in its pure form and is also not recommended for children under the age of 3. Do not confuse it with the essential oil of lemon eucalyptus either (easy to do). Lemon eucalyptus oil has a different mode of action, simply creating a powerful smell to override that of CO2.