Scratching a mosquito bite makes the skin inflamed, and the inflammation makes the skin more itchy. Here’s what mosquito bites itch and what you can do about it. (Kanachai photo, Adobe)
Estimated reading time: 5-6 minutes
ATLANTA – If you’ve ever been bitten by a mosquito, you know how frustrating their bites can be. The small red bumps swell almost immediately, causing an itch that only seems to get worse once you start scratching. The more you scratch, the more they itch — starting a vicious cycle that can leave you irritated, sore, and covered in red bumps.
Some people seem to be mosquito magnets — the bugs come to them wherever they are and leave bites in any exposed flesh — while others remain relatively unharmed and itch-free.
How do mosquitoes choose their prey and how can we repel them? We spoke to some experts for their advice.
Why does a mosquito bite itch?
When a mosquito stings you, it pierces the skin with a special mouthpiece (proboscis) to suck blood. As the mosquito feeds on your blood, it injects saliva into your skin, according to the U.S. Centers for Disease Control and Prevention.
Leslie Vosshall, vice president and scientific director of the Howard Hughes Medical Institute, explained that a mosquito’s saliva has a quality similar to that of an anesthetic, so you don’t feel the bite until after the insect has flown away. It also has anticoagulants so your blood continues to flow without clotting.
“Mosquito saliva contains a lot of proteins, some of which are allergens,” said Vosshall, adding, “Our bodies recognize the mosquito protein as foreign, and our immune cells spring into action to try to fight it.”
Our bodies recognize the mosquito protein as foreign and our immune cells spring into action to try and fight it.
—Leslie Vosshall, Howard Hughes Medical Institute
It’s not the bite that causes the itch — it’s actually the body’s response to the foreign mosquito protein it’s trying to fight off. That’s why some people have only a mild reaction to bites, while others, who are more sensitive to the foreign protein, react with large swellings that are more painful.
And you don’t have to get mad at male mosquitoes, because only female mosquitoes sting. They bite to get a blood meal, as most female mosquitoes cannot produce eggs without that blood.
How do mosquitoes choose their prey?
Like most other blood-feeding insects, mosquitoes can smell us from afar because of the carbon dioxide we exhale, which is why they come in the first place, according to Daniel Markowski, technical adviser to the American Mosquito Control Association.
“Once they actually get close to a host, they use a variety of other signals to eventually hone in,” he said. “These include visual components such as shapes, sizes and colors. Therefore, dark colors are not recommended in prime skeeter habitats as they stand out more, especially with regard to backgrounds and contrasts.”
Other chemical cues “including breath odors, microbiota byproducts on our skin or other common human odors such as octenol, ammonia, caproic acid or lactic acid” all combine with our carbon dioxide to make us more or less attractive to different mosquito species, he added. .
It’s probably a combination of a person’s carbon dioxide and other odors that attracts mosquitoes, said VosshalI, who recently wrote an article on “The Unbreakable Attraction of Mosquitoes on Humans.” But she said the jury is still out on what exactly makes one person more attractive to a mosquito than another.
“This is something we’re working on — the amount and type of body odor a person gives off is probably the reason,” Vosshall said via email. “There are papers that claim it’s blood type, or sweetness in the blood, or sex (women are supposedly more attractive to mosquitoes), but nothing has been conclusively proven.”
What counters the urge to scratch?
“Don’t scratch” is the advice most experts and health professionals give. As harsh and sometimes unrealistic as it sounds, scratching makes the skin inflamed and the inflammation makes the skin more itchy.
“Scratching can also cause secondary infections and prolong irritation,” Markowski warned, adding that in extreme cases, people can scar themselves.
Instead, there are dozens of creams and sprays that promise itch relief, as well as home remedies and mosquito repellents, so choosing what’s right for you can often come down to trial and error.
“In general, all the different anti-itch creams are very similar,” Markowski said. “In general, I suggest that if you are highly allergic to mosquitoes, you may need a cream containing Benadryl or a similar antihistamine.”
Vosshall recommended applying hot water to the bite as soon as possible.
“Very hot water — as hot as you can tolerate it, but not so hot that you burn yourself — short-circuits the itch reflex,” she said.
“If you’re out walking and that’s not practical, a lidocaine topical anesthetic gel can be helpful to prevent the itchy feeling, as can an over-the-counter cortisone cream.”
While both experts said many people prefer natural remedies or herbal products, they urged caution. There is no scientific evidence that these remedies work, and they may have their own precautions or side effects.
In fact, the best remedy to combat the itch is to prevent a bite in the first place.
“Chemical repellents, including DEET or picaridin, are safe and highly effective,” Vosshall said. Markowski agreed, describing DEET as the “gold standard,” registered with the Environmental Protection Agency and approved by the CDC.
However, he acknowledged some people’s concerns about the ingredient’s toxicity, adding: “As with all products, I would suggest treating a small area first and making sure you don’t have any allergic reactions. Also make sure you read and follow the label all use guidelines.”
For a comprehensive guide to repellents, the CDC lists EPA-registered options on its website, and the EPA site includes a search function to help you find the right one.
When to call for medical help?
Some people can have severe allergic reactions to mosquitoes, although it’s rare in practice, Vosshall said. If you experience severe symptoms such as hives, difficulty breathing, or anaphylaxis, you should seek immediate medical attention.
You should also consult a doctor if you plan to travel to a country where blood-borne pathogens such as Zika virus and malaria are common. Mosquitoes can spread some diseases from person to person, but a doctor can advise whether vaccines or preventative treatments are available.