The scenario plays out every summer. You’re enjoying a beautiful day outside when suddenly, a red, itchy welt rises up on your skin. Without thinking – or even knowing why mosquito bites itch – you instinctively start to scratch. Your skin reddens, the bite gets itchier, and you start to notice two more red welts appearing from new bites. Your day just got a lot more annoying. So, why does this happen? Why are mosquito bites itchy?

Why do mosquito bites itch?

When a mosquito bites you, a few things happen. For starters, the mosquito uses her (all mosquitoes that bite are female) 6 needle-like stylets to bite. 4 of these stylets consist of a pair of mandibles that saw the skin and a pair of maxillae that hold the skin back during the process. Once she breaks through your skin, the mosquito quickly searches for a blood vessel and then begins the blood-siphoning process. Mosquitoes can suck your blood through the labrum with such force that tiny blood vessels collapse or rupture. At the same time your blood is pumping out of your body, the mosquito pumps saliva in via the hypopharynx.

This saliva contains several compounds. One of these compounds acts as an anticoagulant, which prevents your blood from clotting at the site of the puncture, while another acts as an analgesic which prevents pain during the bite This allows the mosquito to feed quickly, giving her a better chance of stealing away with your blood before you notice and splat her on your arm. Their saliva is specifically why mosquito bites itch – you have an allergic reaction to it, resulting in the telltale bump and itching associated with mosquito bites.

arm itching with lots of mosquito bites

The science behind what causes mosquito bites to itch

As mentioned, the mosquito saliva flows into your body through one tube (the hypopharynx) while another tube (the labrum) is used to pump your blood up to the waiting mosquito. The saliva contains enzymes and proteins that bypass your body’s natural coagulation system. These anticoagulants – along with up to 19 other enzymes and proteins – directly cause the allergic reaction in your body.

Your body’s immune system responds to these allergens by releasing histamines. This sensitization is responsible for your body sending immunoglobulins to the mosquito bite. Immunoglobulins break down connective tissue and mast cells, which actually release the histamines that make mosquito bites itchy. Mast cells help heal wounds and defend against pathogens, but they play a big part in allergic reactions and inflammation. The histamines they release are commonly combated with antihistamines, which work to stop the itch.

New research points to a more complicated response from the body that includes a ‟histamine-independent peripheral pathway.” This involves mast cells as well, but theorizes that substances other than histamines are released, which then cause peripheral neurons to signal the central nervous system (CNS). The CNS interprets these signals and sends them to the brain, which lets you know that the mosquito bite itches.

When you scratch a mosquito bite, it may provide temporary relief because it helps to reduce the itchiness that is associated with the bite. Scratching stimulates nerve endings in the skin which send signals to the brain to override the sensation of itching. However, this relief is often short-lived and can actually make the itching worse in the long run.

More pressing matters than why mosquito bites itch

The science behind why mosquito bites itch is interesting, to say the least, but that doesn’t help you once you’ve been bitten. The bite will still puff up, turn red, and itch. Chances are, you’ll oblige the itch and scratch until your heart’s content. Unfortunately, you might also scratch until you break the skin, depositing dirt or other contaminants into the open wound. This can lead to bacterial infections.

And even if you don’t cause your own infection, mosquitoes might do the dirty work for you. These flying pests can carry and transmit multiple diseases – some deadly – such as malaria, dengue, Chikungunya, yellow fever, and mosquito-borne encephalitis.

How to stop the itch

When it comes to treating an itchy mosquito bite, the first step is to clean the affected area with soap and water to reduce the risk of infection. You can also apply a cold compress or ice pack to the bite to reduce swelling and numb the area. Over-the-counter creams and ointments containing hydrocortisone or calamine can also be used to alleviate itching and reduce inflammation. In addition, taking an antihistamine can help to relieve the itchiness associated with mosquito bites. If you develop a fever, headache, or any other unusual symptoms after a mosquito bite, it is important to seek medical attention.

How long do mosquito bites last

Mosquito bites can itch for anywhere from a few days to a couple of weeks, depending on the individual's reaction to the bite and the size of the bite. The larger the bite, the more likely it is to itch for a longer period of time. Additionally, if an individual has a more severe allergic reaction to the mosquito bite, it could take longer for the itching to subside.

Now that you know what causes mosquito bites to itch and what might happen, it’s time to do something about it. Call your local Terminix technician to help lower the population of mosquitoes around your property – ensuring that you and your family can enjoy the great outdoors.