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Humans are "always in a perpetual war" against mosquitoes, stated Dr. Conor McMeniman, an assistant professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health and the Johns Hopkins Malaria Research Center in Baltimore, 

Speaking to CNN, McMeniman explains how and why some mosquitoes stick more than others. 

Mosquitoes kill more humans than any other animal because they carry illnesses such as malaria, dengue fever, and West Nile virus.

Read more: Ecuador to release sterile mosquitoes in Galapagos to fight disease

Even when they do not carry disease, they are still a nuisance, and here are what scientists believe is causing them to come back.

Mosquitoes consume plant nectars and fluids and even aid in flower pollination. When it comes time for female mosquitoes to lay eggs, they require extra protein, which they obtain by swallowing blood. 

According to McMeniman, it's best for the mosquito to drink the blood quickly and fly away, and to do this they spit into the skin "in a whole cocktail of different proteins," that act as painkillers and anticoagulants that keep the blood from clotting."

Itching and discomfort from mosquito bites, caused by our body's inflammatory response to this cocktail, appear just after the culprit has been swatted.

Individuals react differently to mosquito bites; one person may only get a few pimple-like spots, while others seem to be dealing with coin-sized blisters for days. 

According to McMeniman, “How attractive you think you are to mosquitoes might not necessarily correlate with how attractive you actually are to the mosquitoes,” adding that “Some of that is driven by the perception of your reaction to the mosquitoes and whether you’re itching.”

What attracts mosquitoes to you?

McMeniman has found that some people really are mosquito magnets, and he’s documented it in his recent study in the journal Current Biology. Mosquitoes responded differently to the array of chemicals making up each individual’s body odor bouquet, and they deem some more appetizing than others. Unfortunately, homing in on what makes some people extra appealing to mosquitoes isn’t a simple matter.

“There could be a variety of factors that might influence the composition of your scent,” McMeniman explained, adding that underlying diet, genetics, and physiology all have the potential to influence a mosquito's decision to bite someone. The doctor also noted that the chemistry of the process is still not fully clear. 

He detailed how “First they smell you, then they see you, and then when they’re close enough, maybe within a meter of the host, they can actually detect thermal cues dissipating from your skin." Additionally, carbon dioxide, the gas we exhale when breathing, is a crucial scent that draws mosquitoes to us.

Once you're itchy, it's too late

According to Dr. Kristen Healy, an associate professor of entomology at Louisiana State University and president of the American Mosquito Control Association, body sweat, and heat also seem to increase the amount of mosquitoes around. 

“If I’m active and I’m sweating, I definitely will notice a difference in mosquito attraction because they can cue into those other extra odors,” Healy stated.

A number of scientific studies have pointed to potential keys to mosquito attractiveness over the years — some have claimed that individuals who drink beer are more likely to get bitten, while others have suggested that certain colors, notably red, may be more appealing to mosquitoes.

Read next: Mosquitoes Caught in Smart Traps

Healy adds that not all devices and sprays that claim to drive away mosquitoes actually do. She notes that ultrasonic mosquito gadgets are "not necessarily backed by research and science, and they're just out there on the market." She adds that she would never trust a product that claims it can repel mosquitoes with 100% effectiveness.

McMeniman also pointed to the dangers of insect repellents over larger areas. Although they may be effective, they are like "walking around in a cloud of insecticide."

However, bug spray and covering up more in the summer can sometimes be protection enough according to both Healy and McMeniman. McMeniman also recommends oil of lemon eucalyptus for those who prefer products without harsh chemicals.