The Weird Reason Your Mosquito Bites Itch for So Long

Updated: Jun. 22, 2022

During summer, one of the main ways people burn calories is scratching mosquito bites. OK, that's not true, but it sure feels that way—and here's why.

Mosquito biting in the arm is a cause of malaria.SIM ONE/ShutterstockMosquito bites are like a rite of passage in the summer (particularly if you live here, named the most mosquito-infested city in America!). Whether you’re hiking in the woods or out on a patio trying to enjoy a cocktail, it seems that you end up with one or ten bites—daily. While there are some excellent ways to minimize that itch, why do the darn bites have to be so bothersome?

“When mosquitos bite you, they inject a bit of saliva,” says Bernard Cohen, MD, professor of dermatology at the Johns Hopkins University School of Medicine. “For most of us, it triggers a reaction. You get red, swollen, and it itches like crazy,” he explains. There are other people who aren’t so lucky—they actually experience an extreme allergic reaction known as anaphylaxis—they get hives and their airways swell shut, requiring emergency intervention, stat.

But even if you’re not dangerously allergic, you could still be mildly allergic if your bites stay itchy for days, according to Xinzhong Dong, PhD, a professor of neuroscience at Johns Hopkins Medicine. He notes that some people are slightly more allergic to the saliva than others, and the itch persists longer. Find out the 10 reasons why you’re getting bitten—and what you can do about it.

Dong believes that there could be another reason your itch is so persistent. “There’s a theory that if you scratch the bite a lot, it damages the epidermis and you get a secondary infection.”

According to Cohen, where you are bitten can make a difference. Bites on the extremities—including the hands or feet—last longer than those in areas like the upper arms and thighs.

If you’re going to be out this summer, Cohen suggests wearing bug repellent that contains DEET (up to 30 percent). That will protect you for about four hours, so don’t forget to reapply.

For extra protection try these mosquito-repelling products you’ll actually want to use. If you want to avoid bug bites without using chemicals, try these natural ways to repel mosquitos and make sure your backyard is filled with these plants that help keep mosquitos away.