Inflammation

Redness, swelling, heat, and pain in a tissue due to injury or infection. When body tissues become damaged, mast cells release the chemical histamine and other substances. Histamine increases the flow of blood to the damaged tissue and also makes the blood capillaries more leaky; fluid then oozes out and into the tissues, causing localized swelling. Pain is caused by the stimulation of nerve endings by the inflammatory chemicals. Inflammation is usually accompanied by a local increase in the number of white blood cells. These cells help to destroy any invading microorganisms and are involved in repairing the damaged tissue. Inappropriate inflammation (as in rheumatoid arthritis and some other autoimmune disorders) may be suppressed by corticosteroid drugs or by nonsteroidal anti-inflammatory drugs.