Why do mosquito bites itch so badly? And why do they swell?! If you are wondering how such a small insect can cause such incessant itching and swelling, the first thing to know is that mosquitoes don’t actually bite you. Instead, mosquitoes have a long tube attached to their mouth called a proboscis that they stab into their host and use to suck out blood like straw!
Mosquitoes also have special hematophagous arthropod saliva in their proboscis. Hematophagous arthropod saliva is a scientific way of saying “spit from a blood-sucking creature with an exoskeleton.” This specific type of saliva has chemicals and proteins in it that prevents blood from clotting. So what do mosquitoes do with their hematophagous arthropod saliva? They inject it into their victim before they start sucking its blood to prevent any clotting while they slurp.
Therefore, the itching that you experience after a mosquito bite is your body reacting to the mosquito’s saliva. After detecting the saliva in your system, your body immediately sends antibodies to fight this foreign substance. In essence, you experience an allergic reaction to the mosquito saliva, causing itching and inflammation. Depending on how allergic your body is to mosquito saliva, the swelling and itching can last anywhere from a few hours to a full week.