Mosquito bites swell because when a mosquito injects saliva into the skin while feeding, the immune system recognizes the saliva as a foreign substance. In response, the body releases histamine and other chemicals to fight off the intruder. Histamine increases blood flow and causes white blood cells to accumulate around the bite area, leading to localized inflammation or swelling. It also activates nerve endings, causing itchiness. This immune reaction is similar to an allergic response and results in the characteristic raised, itchy bump after a mosquito bite.
In some cases, people may experience a more severe allergic reaction known as Skeeter Syndrome, where the swelling, redness, and pain are much more intense due to a strong immune response to proteins in the mosquito's saliva. This can cause large, painful, and swollen areas that last longer than typical bites.
