An insect bite may result in the inflammation of that spot. This is triggered by the chemicals such as
histamines
Inflammation is the body's way of self-protection. When inflammation occurs, chemicals like histamine are released from the body's mast cells. Histamine increases blood flow to the area and the leakage of fluid and proteins from the blood into the tissue space. Thus, the quick release of histamine produces the redness and swelling associated with inflammation.