Scientific research has shown that mosquitoes bite some people more than others for several reasons, including the smells that those people give off, the chemicals on those people's skin and even how much carbon dioxide they emit while breathing. Experts estimate that mosquitoes are highly attracted to about 10 percent of all people, with those people's genetics accounting for about 85 percent of their attractiveness to mosquitoes. Other research suggests that people who are less attractive to mosquitoes emit smells and chemicals that repel the insects. As of 2012, there still was much that was not known about why mosquitoes bite some people more than others and what the people who are bitten more can do about it.
Why Mosquitoes Bite
Only female mosquitoes bite people. They do it for the blood, which contains protein and nutrients that they need either to produce eggs at all or to produce a larger batch of eggs. Before each time they produce a batch of eggs, they will seek out a blood meal. For regular meals, they feed on nectar and other juices produced by plants.
A female mosquito begins locating prey by detecting carbon dioxide, which is emitted by animals when they exhale and through their skin. The mosquito uses an antenna-like structure called a maxillary palp to detect carbon dioxide from as far as 164 feet (50 m) away. At closer distances, it uses a feathery antenna to identify certain chemicals, and its nose is perforated with many tiny holes that the odors in the air can penetrate. After the mosquito has found a concentration of carbon dioxide being emitted by a person, the mosquito's sensory receptors tell it whether the combination of chemicals and odors being emitted by that person make him or her suitable prey.
Substances That Attract
Research suggests that, in addition to carbon dioxide, some of the substances that people produce and that attract mosquitoes are sweat, lactic acid, uric acid and a chemical called octenol. Lactic acid is emitted through the skin, especially during exercise. Uric acid is a product of the body metabolizing certain proteins, and most of it is excreted in urine, but excess uric acid can build up under the skin. Octenol is present in a person's sweat and breath.
Some people produce greater quantities of these substances, so mosquitoes bite some people more than others. Very large people and pregnant women generally breathe out more carbon dioxide, so they tend to be bitten more often. People who exercise outdoors produce more lactic acid, sweat more and breathe more heavily, so they also tend to suffer more mosquito bites. Many perfumes and deodorants that people to mask their natural body odors also are believed to be attractive to mosquitoes.
Substances that Repel
Commercial mosquito repellants contain various chemicals — such as N,N-diethyl-meta-toluamide, better known as DEET — that are believed to turn away mosquitoes by masking the user's body chemicals or by inhibiting the insects' sensory organs. Some research suggests, however, that certain substances already found on certain people's skin make those people less attractive to mosquitoes. Two such chemicals are known as geranyl acetone and 6-methyl-5-hepten-2-one. Scientists have looked into the origin of these chemicals — namely, whether they are produced by the body, obtained from the environment or a combination of those methods. The existence of these chemicals found on some people's skin suggests that mosquitoes bite some people more than others not only because some people are more attractive to mosquitoes, but also because some people naturally repel them.