Inflammation is one of the many ways the body knows how to protect itself. When something becomes inflamed it turns red, swollen, hot, and painful. These signs mean that white blood cells are trying to get rid of harmful invaders in the body. You can think of it as a response to infection. This increases blood flow to the affected area, causing redness and warmth. While it can be painful, it is not always painful. If an exterior wound looks inflamed you should seek immediate treatment. Wounds act as a doorway to infection as it allows foreign invaders into areas they would not otherwise have access to.
Sometimes the body's defense mechanism triggers inflammation when there are no foreign bodies to fight off. This is what happens with autoimmune diseases such as arthritis. Arthritis is a general term for inflammation of the joints. It is not connected with fighting infection. This chronic inflammation is extremely painful and causes joint stiffness, pain, and loss of function in the joints.