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The Buzz

Nature Curiosity: Why Do Mosquito Bites Itch?

(Photo via Shutterstock)

Most everyone has had a perfectly pleasant summer day or evening ruined by the constant swatting of mosquitoes in hopes of avoiding the itchy aftermath.

So why do the bites itch anyway? It's actually an allergic reaction, according to the Illinois Department of Public Health. When a mosquito bites, it pierces the skin of its victim, and saliva from the mosquito enters our bloodstream. 

The mosquito's saliva is interpreted as a foreign substance by your immune system, so it gears up to combat it, releasing histamine, which in turn causes the itchy, red bumps so familiar to us as mosquito bites, according to the American Academy of Allergy, Asthma and Immunology

To develop a reaction to the bite, contact must last at least six seconds, the academy reports. And the itching may not be immediate. It can take a few hours or even a few days to develop.

However, not everyone experiences the same type of reaction to a mosquito bite. People who have never been bitten — those lucky souls! — may not have any reaction, while others may have more serious reactions, including large lesions, hives, fever, joint swelling and even anaphylaxis – a life-threatening allergic response that can cause a drop in blood pressure and block breathing. 

Only female mosquitoes bite, because they require a meal of blood before they can lay their eggs, according to the Illinois Department of Public Health. They are able to hone in on us by detecting the carbon dioxide we exhale along with body heat and body chemicals such as lactic acid in our perspiration. And everyone knows someone — or is someone — who mosquitoes particularly love to feast on, although scientists do not fully understand why.

Just about everyone has heard an old wives' tale about how to get a mosquito bite to stop itching. Some people put an X on the itchy bite with their fingernail; others place the back of a hot spoon on it for some relief. And even though those tricks may provide some relief, the American Academy of Allergy, Asthma and Immunology recommends over-the-counter anti-itch lotions or, if those don't help, using a topical steroid such as hydrocortisone or oral antihistamines. An ice pack can also reduce the discomfort. 

While mosquito bites are an itchy nuisance for most of us, they can also transmit deadly and potentially serious diseases. In fact, the mosquito is the most dangerous animal in the world, according to the Illinois Department of Public Health. Mosquitoes transmitting malaria kill 2 million to 3 million people each year worldwide and infect an additional 200 million people annually.  

Here in Illinois, the main disease risks from mosquitoes are West Nile virus and several strains of encephalitis, according to the state health department. While these illnesses are not as widespread as malaria is elsewhere in the world, they are serious nonetheless. As a result, people should take steps to avoid mosquito bites.

To prevent bites, the U.S. Centers for Disease Control and Prevention recommends wearing long sleeves and long pants whenever possible and using an insect repellent containing DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol or 2-undecanone. 

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