The insult could be a scrape or a reaction to something like a mosquito bite or flea bite. Inflammation is simply the cell's defense mechanism. One of the cell's reactions is to produce compounds that attempt to protect it and some of its neighbors. Those compounds are made from fatty acids and are called eicosanoids. The eicosanoids that are made from omega-6s attract many white blood cells to the site, and produce much of the pain and itching associated with the mosquito bite.
Platelets collect in an attempt to stop bleeding.
The visible signs of inflammation are redness, swelling, heat, and pain, all in varying degrees. We've all had those symptoms from our different bites and scrapes. All that blood brings warmth to the site. Some inflammation is good, and a natural response. But sometimes the body can get out of hand with its reactions.