Lisa Kaley, age 12, of Gary, Indiana, for her question:
What causes the pain and swelling from mosquito bites?
The flying mosquitos depart from the scene in the fall, but not before they have left offspring to pester our lives next summer. These youthful mosquitos spend the winter in water. Some are fierce little wrigglers, devouring all sorts of creatures in the streams and ponds. Sooner or later all of them become pupae, clinging to the surface, under the ice or sleeping in soggy swamps. Come spring, they hatch into winged adults and we can expect the pesky mosquito season to start.
An angry yellowjacket uses her sting as a weapon. So do bees and most other stinging insects. But not a mosquito. She is not angry and means no harm to her victims. The pesky creature is merely hungry and the damage she does is not part of her plan. She must live on a liquid diet. Her beak is strong enough to pierce the skin so that she can sip up a tummy full of rich, warm human blood. The male mosquito has a weaker beak so he must live on juices from tender plants.
When the blood oozes from even a tiny puncture, it thickens and clots to seal the wound. A mosquito's siphon is so small that she cannot sip thick, clotting blood. But she came prepared with a chemical to stop the clotting, plus a special little tool to inject it. This substance seeps through the tissue around her stab wound and gives her time to sip a meal of runny, red blood. However, her anti clotting injection soon begins to work chemical havoc in the tissue.
The trouble is caused by a histamine, one of the complex chemicals related to allergies. The body makes histamin in tiny traces and as long as they stay inside the living cells they seem to caus o trouble. But in larger amounts, say one part per million, they can cause chemical havoc. They weaken and permeate the walls of cells and capillaries. Each cell, we know, is a living unit of electrochemical activities. When these packages ar broken apart, their busy ingredients make a wish mash of the surrounding tissue.
The mosquito injects a histamine type chemical that stops the blood from clotting to seal the puncture. It permeates through the tissue, causing blood to ooze from weakened capillaries. The area becomes red and itchy. When the cells are attacked, the well organized tissue becomes a disrupted mess of fluids and biochemicals. The area swells up and becomes itchy and inflamed.
The tissue around a mosquito bite may be completely disorganized. No wonder it itches and stings. Usually it takes a week or more to repair the damage. However, some people are allergic and extra sensitive to certain histamines. In rare cases, an ordinary mosquito may cause a very severe reaction and the patient needs medical attention. These people often have serious allergies to bee stings and various other histamines.