Why Do Mosquito Bites Itch?

It may seem that the tiny puncture from a mosquito “bite” and the small amount of blood taken from the body wouldn’t be enough to cause problems for a healthy human being. Mosquitoes are so small it would seem that we shouldn’t even notice. But the truth is mosquito bites do get our attention, especially for some time after the bite actually occurs.

Apart from the bite itself, which is uncomfortable, the sensations after the bite are a problem. When the mosquito sticks the “needle” into our skin, the natural juices from the mosquito contain several different chemicals (enzymes and chemicals that keep blood from coagulating). In fact, the “bite” is so small and causes so little sensation we may not feel it when it happens. Many people don’t experience itching and swelling with the first mosquito bite.

However, human beings bitten by a mosquito several times eventually become sensitive to these foreign substances. Some people may become insensitive to bites over time, while others actually become more sensitive. In addition to the redness of skin, small bumps and slight itching sensation, people who are more sensitive can develop blisters and wider areas of inflammation.

One of the best ways to understand why a mosquito bite itches is to think about allergies in general. We can get a similar feeling if we are allergic to some types of soap, detergent, deodorant and even food we eat. Almost anything can be included in the allergen category – dust and pollen commonly cause such reactions, as are some medications and cat dander.

Our bodies react to foreign substances with what is commonly known as the histamine response. This natural substance makes the small blood vessels more permeable so that white blood cells and proteins can attack the foreign substance in that area. This chemical reaction is a primary cause for the inflammation and swelling around a bite or other injury to the skin. Chemicals and hormones called mediators are released, helping to put more white blood cells into action. Histamine is perhaps the best known of the mediator substances.

Allergic reactions are basically the way that our bodies respond to a substance that has invaded. These are referred to as antigens. Histamine production in the area of the invasion is part of immune-system response, which exists to protect us from toxic substances, harmful bacteria etc. Reactions can occur in one spot, such as with a mosquito bite, or over larger areas of the body. The term for the overall process is called sensitization when white blood cells produce a specific antibody for a particular antigen.