<h3>The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability</h3><h3> of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane.</h3>
If it is the abdomen and not the stomach area i would say its from the heat. if you've ever seen a dead animal on the side of the road over the course of a few days, they start to swell from the sun beating down on them all day.
