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How and Why a Mosquito Bites You

August 08, 2015

Story at-a-glance

  • Female mosquitoes feed on human blood, not for their own nutritional purposes but in order to produce their eggs
  • The mosquito has a mouthpart called a proboscis, which is like a hypodermic needle.
  • She uses the proboscis to pierce your skin and probe around until she finds a capillary to suck the blood from
  • While biting, mosquitoes inject saliva into your body to stop your blood from coagulating; this is the point at which she can transmit diseases directly into your bloodstream

By Dr. Mercola

Mosquitoes are one of the few annoyances of summer. To be fair, they do serve a purpose in the environment. Mosquito larvae are a popular snack for fish and other aquatic creatures while adult mosquitoes provide food for birds, bats, and spiders.

Male mosquitoes don't bite humans, but rather feed off flower nectar. Female mosquitoes are the ones that require meals of blood in order to develop and lay eggs.

Their bites are at best an itchy nuisance and, at worst, can transmit serious diseases like malaria, yellow fever, dengue, encephalitis, chikungunya, and West Nile virus. Mosquitoes can even spread Lyme disease!

In certain parts of the world, a child dies every minute from mosquito-transmitted malaria. No wonder mosquitoes have been described as the "world's deadliest animal…"1

How and Why Mosquitoes Bite

Female mosquitoes feed on human blood, but not for their own nutritional purposes. They need the protein and other components in the blood to produce their eggs.

The mosquito has a mouthpart called a proboscis, which is like a hypodermic needle. She uses it to pierce your skin and probe around a bit until she finds a capillary to suck the blood from.

She also injects some of her own saliva, which stops the blood from coagulating but is also the point at which she can transmit diseases directly into your bloodstream.2

She then sucks the blood out and into her abdomen, where it becomes digested and used to produce eggs. In the video below, you can see a close-up view of an Anopheles gambiae mosquito feeding on a capillary (don't watch if you're squeamish).3

Some People May Be 'Invisible' to Mosquitoes

Certain compounds emitted through sweat and produced by bacteria on human skin are irresistible to mosquitoes. Lactic acid, for instance, which is commonly found in human sweat, attracted about 90 percent of the mosquitoes in one test.

However, when other naturally occurring chemical compounds, such as 1-methylpiperazine, were released, they blocked the mosquitoes' sense of smell so effectively that the mosquitoes were oblivious to a human hand nearby.

According to a presentation given at the 246th National Meeting & Exposition of the American Chemical Society by Ulrich Bernier, Ph.D., a chemist at the US Department of Agriculture (USDA) Mosquito and Fly Research Unit. Bernier explained:4

"If you put your hand in a cage of mosquitoes where we have released some of these inhibitors, almost all just sit on the back wall and don't even recognize that the hand is in there. We call that anosmia or hyposmia, the inability to sense smells or a reduced ability to sense smells."

Certain people seem to secrete more of these natural substances than others, making them essentially invisible to mosquitoes. Insect sprays containing 1-methylpiperzine are in the works, but so far scientists haven't been able to figure out how to keep the substance from evaporating off of the skin, as naturally occurs over time.

Why Do Some People Get Bitten More Than Others?

New research from the London School of Hygiene & Tropical Medicine (LSHTM) suggests how attractive you are to mosquitoes may be genetically based, in particular related to your genes' control over your body odor.5

In a study using twins, either identical or fraternal, the identical twins, who are genetically identical, experienced a similar number of mosquito bites while non-identical twins had a larger disparity.6

It's been suggested that 85 percent of your susceptibility to mosquito bites may be due to genetics, but there are other factors as well. For instance, movement and heat attract mosquitoes, and mosquito bites are more common among:7

People with high concentrations of steroids or cholesterol on their skin surfacePeople who produce excess amounts of uric acid
People who give off more carbon dioxide, including pregnant women and those who are larger or overweightPeople with Type O blood8
People who are exercising, as this increases sweat, heat, lactic acid, and movement, all factors that lure in mosquitoesBeer drinkers (for reasons that remain a mystery, drinking alcohol stimulates mosquito attraction)9

DEET-Containing Insect Repellents Are Better Off Avoided

Conventional insect repellents typically contain DEET, a chemical that smells unpleasant to mosquitoes so they stay away. The trouble is some mosquitoes have developed resistance, making DEET less effective than it used to be. And, this chemical is linked to a number of very serious side effects.

DEET (N,N-diethyl-meta-toluamide) is used in more than 230 different products –  in concentrations of up to an astounding 100 percent. If a chemical melts plastic or fishing line, it's not wise to apply it to your skin – and that is exactly what DEET does.

Duke University Medical Center pharmacologist Mohamed Abou-Donia spent 30 years researching the effects of pesticides. He discovered that prolonged exposure to DEET may impair cell function in parts of your brain – demonstrated in the lab by death and behavioral changes in rats with frequent or prolonged DEET use.

Children are particularly at risk for subtle brain changes because their skin more readily absorbs chemicals in the environment and chemicals more potently affect their developing nervous systems. Other potential side effects DEET exposure include:

Memory loss HeadacheMuscle weakness and fatigue
Shortness of breathMuscle and joint painTremors

Are There Any Natural Mosquito Repellents?

You can avoid many bites by staying inside around dawn and dusk, which is when mosquitoes are most active. If you must be out during those times, wear light-colored, long-sleeved shirts and long pants, hats, and socks (some mosquitoes are more attracted to dark clothing and can bite through tight-fitting clothes). Mosquitoes are also thicker in shrubby areas and near standing water.

As mentioned, body temperature and skin chemicals like lactic acid also attract mosquitoes, which explains why you're more likely to be "eaten alive" when you're sweaty, such as during or after exercise, so trying to stay as cool and dry as you can may help to some degree.

Some experts also recommend supplementing with one vitamin B1 tablet a day from April through October, and then adding 100 mg of B1 to a B100 Complex daily during the mosquito season to make you less attractive to mosquitoes. Regularly consuming garlic may also help protect against both mosquito bites, as may the following natural insect repellents:

How to Make Your Backyard Less Hospitable to Mosquitoes

If mosquitoes are an issue in your own backyard, there are some steps you can take to encourage them to live elsewhere. Draining standing water, including pet bowls, gutters, garbage and recycling bins, spare tires, bird baths, children's toys, and so on, is important. This is where mosquitoes breed, so if you eliminate standing water you'll eliminate many mosquitoes.

Planting marigolds around your yard also works as a bug repellent because the flowers give off a fragrance that bugs do not like. This is a great way to ward off mosquitoes without using chemical insecticides. A simple house fan could also help keep mosquitoes at bay if you're having a get-together in your backyard or, for a longer-term solution, try installing a bat house (bats are voracious consumers of insects, especially mosquitoes).

It's best to avoid using bug zappers in your yard, as these may actually attract more mosquitoes while killing beneficial insects. Insect foggers designed to clear insects out of your backyard should also be avoided, as they require the use of strong, potentially harmful, pesticides and don't offer lasting protection. Even those clip-on repellents and fans that are widely sold are best avoided, as they contain even more toxic ingredients than repellents that can be applied to your skin, and they pose an inhalation hazard.12

Previous ArticleDocumentary About Your Body’s Chemical Burden Next ArticleInspiring Account of How to Put Rheumatoid Arthritis into Remission

Sources and References

  • 1 GatesNotes April 25, 2014
  • 2 BBC News July 24, 2015
  • 3 PLOS One December 13, 2012
  • 4 EurekAlert September 9, 2013
  • 5 Newsweek May 1, 2015
  • 6 PLOS One April 22, 2015
  • 7 WebMD Are You a Mosquito Magnet?
  • 8 J Med Entomol. 2004 Jul;41(4):796-9.
  • 9 J Am Mosq Control Assoc. 2002 Jun;18(2):91-6.
  • 10 J Agric Food Chem. 2004 Jul 14;52(14):4395-400.
  • 11 Science Daily August 28, 2001
  • 12 Environmental Working Group, Bug Repellents Report (PDF)
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