Inflammation is the body’s immune response, protecting us from foreign substances such as bacteria or viruses. In autoimmune diseases, inflammation is caused by the body attacking its own cells and is often chronic. However, normally inflammation is acute.
Essentially, it is the dilation of arteries as immune cells and nutrients rush to the affected area. White blood cells ingest the foreign invaders. When the die, they create pus which creates swelling. This swelling can compress nerve endings, causing pain.