Why do Mosquito Bites Itch? The Science of Summer

Brain freeze, sunburns, and bug bites -- welcome to summer! While summer in the Northern Hemisphere often conjures up images of swimming pools and beach umbrellas, it also comes with a few pains. While scientists can't make them go away (yet), they can at least tell us why we have to suffer through them! Maybe brain freeze, sunburns, and itchy bug bites can somehow be a good thing?

What causes brain freeze?

About one-third of the population is susceptible to ice cream headaches, or brain freeze. When consuming ice cream or cold beverages too quickly, the cold can trigger a sudden, painful headache that lasts for a few minutes. As it turns out, this is just the brain trying to protect itself!

When something cold hits the roof of your mouth, it triggers the contraction (or shrinking) of two major blood vessels: the internal carotid artery and the anterior cerebral artery. To protect itself from the cold, the brain sends a signal to quickly expand these blood vessels to allow for more blood flow and more heat. Ultimately, the rapid contraction and expansion of blood vessels triggers pain receptors on the outside of your brain and causes that pesky headache!

Need to cure brain freeze fast? Just grab a glass of warm water or, even more quickly, press your tongue against the roof of your mouth. As soon as your mouth is warm and your blood vessels return to normal, the headache will go away.

Credit: Sean Dreilinger

Why do we sunburn?

Spend enough time in the sun, and you will burn. It's common knowledge and a common symptom of summertime, but why does it happen? Much like brain freeze, it's just your body taking care of itself.

Normally, melanin, the pigment that gives skin its color, is the body's natural sunscreen. When skin cells are threatened by sunlight's ultraviolet radiation, melanin rushes in to play defense. (All this extra melanin causes your skin to darken, which is why we tan!) When skin cells receive too much UV radiation, however, there isn't enough melanin to protect it, and the cell is damaged to the point of undergoing apoptosis, or cell death.

As for the redness and pain, you can thank RNA for that. Although RNA (DNA's one-stranded counterpart) often carries the code for proteins, a specific type of non-coding RNA breaks into pieces when its cell is killed by UV rays. Receptors recognize this broken RNA and trigger increased blood flow and inflammation in the area -- i.e. redness and pain. This inflammation helps skin heal and prevents cancer-causing mutations, but it's also a large warning from your body: Apply sunscreen, or stay inside!

While sunscreen protects your skin, sunglasses keep your eyes safe from UV rays! (Credit: Boudewijn Berends)

Why do mosquito bites itch?

Brain freeze, sunburns... what could be worse? Mosquito bites, for one. Female mosquitos bite to harvest protein for their eggs (and ), but the aftermath can leave us itching for hours or days afterward. What is it about mosquito bites, though, that make us so itchy?

As it turns out, it has little to do with the bite at all, but with the mosquito's saliva. While the mosquito is sucking blood, it also injects its saliva into your skin. The saliva's job is to act as an anticoagulant, which prevents blood from clotting, but it has one other unfortunate side effect: Most of the world is allergic to it. It's not the mosquito's bite that causes us to itch: It's our allergic reaction to its saliva.

When confronted with an allergen, the body produces histamine, a protein that calls for inflammation. Blood and white blood cells rush in to fight the "danger", and the area around the bite swells, becomes red, and -- you guessed it -- itches. If mosquito saliva were dangerous, histamine would be great! Sadly, like most allergies, itchy mosquito bites are just your body being a little too protective of itself.

Credit: CDC/ James Gathany

Trivia fact: Histamine is the same protein responsible for itchy eyes and runny noses during pollen season! This is why antihistamine medications can work just as well for bug bites as they do for spring allergies.

Science may not make summer woes any less enjoyable, but at least they aren't a mystery. What other summer science questions do you have?

Stay tuned for articles about autumn and winter science!


  • Dell'Amore, C. (2012, July 11). Mystery Solved: Why We Sunburn. Retrieved July 8, 2015
  • Nordqvist, J. (2015, June 4). Brain Freeze: What Is It? Scientists Explain. Retrieved July 8, 201
  • Shim, W.-S., & Oh, U. (2008). Histamine-induced itch and its relationship with pain. Molecular Pain, 4, 29. doi:10.1186/1744-8069-4-29
  • Wake Forest Baptist Medical Center. (2013, May 22). Neuroscientists explain how the sensation of brain freeze works. ScienceDaily. Retrieved July 8, 2015

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About the Author

Alexis Stempien
SSEC Science Writing Intern, Summer 2015

Alexis specializes in writing, video, and social media. A senior at the University of Michigan, she studies Biopsychology, Cognition, and Neuroscience with a Minor in Writing. Outside of the classroom, she enjoys producing videos for her YouTube channel These Neon Hearts, playing mellophone in the Michigan Marching Band, and enthusiastically explaining science news to everyone around her.