(CNN) — If you’ve ever been bitten by a mosquito, you know how frustrating their bites can be. The little red bumps swell up almost immediately, creating an itch that once you start scratching it only seems to get worse. The more you scratch, the more it itches, starting a vicious cycle that can leave you irritated, sore, and covered in tiny red blisters.
Some people seem to be mosquito magnets: the bugs flock to them wherever they are, leaving bites on exposed flesh, while others are left relatively unscathed 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 bites you, it pierces the skin using a special mouthpart (proboscis) to suck blood. As the mosquito feeds on your blood, it injects saliva into your skin, say the US Centers for Disease Control and Prevention (CDC).
Leslie Vosshall, vice president and chief scientific officer of the Howard Hughes Medical Institute, explained that a mosquito’s saliva has an anesthetic-like quality, so you don’t feel the bite until the insect flies away. It also has anticoagulants to keep your blood flowing without clotting.
“Mosquito saliva contains a lot of proteins; some are allergens,” Vosshall said. “Our body recognizes the mosquito protein as foreign, and our immune cells spring into action to try to fight it off.”
It’s not the bite that causes the itching; it is actually the body’s response to the foreign protein in the mosquito it is trying to combat. This is why some people may only have a mild reaction to the stings, while others, more sensitive to the foreign protein, react with large areas of swelling that are more painful.
And don’t get mad at male mosquitoes as only females bite. They bite to feed on blood, since 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 a great distance through the carbon dioxide we exhale, and that’s what brings them closer in the first place, according to Daniel Markowski, a technical adviser at the American Association for Mosquito Control.
“Once they really get close to a person, they use a variety of other cues to finally focus,” Markowski said. “These include visual components such as shapes, sizes and colours. This is why dark colors are not recommended in prime mosquito habitats because they stand out more, particularly when it comes to backgrounds and contrasts.”
Other chemical cues “including breath odors, byproducts of the microbiota on our skin, or other general human odors like octenol, ammonia, caproic acid, or lactic acid” combine with our carbon dioxide to make us more or less attractive to different species of mosquitoes, he added.
It’s likely a combination of a person’s carbon dioxide and other odors that attract mosquitoes, said VosshalI, who recently wrote an article on “The unbreakable attraction of mosquitoes to humansBut he 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 emits is probably the reason,” Vosshall said by email. “There are papers claiming it’s blood type, or blood sweetness, or gender (supposedly women are more attractive to mosquitoes), but nothing is conclusively proven.”
What counteracts the urge to scratch?
“Don’t scratch” is the advice given by most experts and health professionals. As harsh and sometimes unrealistic as it may seem, scratching inflames the skin, and the inflammation makes the skin itchy more.
“Scratching can also cause secondary infections and prolong irritation,” Markowski said, adding that in extreme cases, people can leave scars.
Instead, there are dozens of creams and sprays that promise to relieve itching, as well as home remedies and mosquito repellants, so choosing what’s right for you often comes down to trial and error.
“In general, all anti-itch creams are very similar,” Markowski said. “In general, I would suggest that if you are severely allergic to mosquitoes, you may need a Benadryl cream or a similar antihistamine.”
Vosshall recommended applying hot water to the bite as soon as possible.
“Very hot water, as hot as you can stand it, but not so hot that you burn yourself, generates a short circuit in the itch reflex,” he said.
“If you’re going hiking and that’s not practical, a topical lidocaine local anesthetic gel may be helpful to prevent the itchy sensation, as well as 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 come with their own precautions or side effects.
In fact, the best remedy for itching is to prevent a bite in the first place.
“Chemical repellants, including DEET wave picaridinthey are safe and highly effective,” Vosshall said. Markowski agreed, describing DEET as the “gold standard,” registered with the US Environmental Protection Agency and endorsed by the CDC.
However, he acknowledged some people’s concerns regarding the ingredient’s toxicity, adding: “As with all products, I would suggest treating a small area at first and making sure you don’t have any allergic reactions. Also, make sure you read the label and follow all usage guidelines.”
For a complete guide to insect repellants, CDC lists EPA-registered options on their website, and the EPA site features a search tool to help you find the right one.
When to seek medical attention?
Some people can have severe allergic reactions to mosquitoes, although in practice it’s rare, Vosshall said. If you experience severe symptoms such as hives, difficulty breathing, or anaphylaxis, you should seek medical attention immediately.
You should also consult a doctor if you plan to travel to a country where bloodborne pathogens, such as Zika virus and malaria, are common. Mosquitoes can transmit some diseases from person to person, but a doctor will be able to advise you if vaccines or preventative treatments are available.