What is inflammation?

Inflammation is a normal response of the body that involves an increase of blood flow to a site of injury. The signs of inflammation are redness (rubor), heat (calor), swelling (tumor) and pain (dolor). One other classic sign is loss of function (function laesa).

Acute inflammation is a dramatic localized response to injury. It comes vascular changes increasing blood flow (hyperemia) to the area that cause the redness and warmth as observed along with swelling. There’s also a cellular component, in which large numbers of white blood cells move to the injury to stop infectious agents and clear debris. The cells that come form what is referred to as an exudates.

Chronic inflammation is when inflammation lasts beyond six weeks (subacute applies to inflammation beyond a week, but not lasting as long as six weeks). A chronic response can last months and years. It is essentially a “standoff” between an injury and the body’s defense. They resist each other, but neither is strong enough to beat the other down.


Nowak TJ, Hanfod AG. Pathophysiology: Concepts and applications for health care professionals, 3rd ed. 2004. New York, McGraw-Hill.

Published by David Despain, MS, CFS

David is a science and health writer living on Long Island, New York. He's written for a variety of publications including Scientific American, Outside Online, the American Society for Nutrition's (ASN) Nutrition Notes Daily, and Institute of Food Technologists' (IFT) Food Technology magazine and Live! blog. He's also covered new findings reported at scientific meetings including Experimental Biology, AAAS, AOCS, CASW, Sigma Xi, IFT, and others on his personal blog "Evolving Health." David is also an active member of organizations including the National Association of Science Writers (NASW), the American Association for the Advancement of Science (AAAS), the American Society for Nutrition, the Institute of Food Technologists, and the National Audubon Society. David has a master's degree in human nutrition from the University of Bridgeport, and a bachelor's degree in English from University of Illinois at Springfield. He also earned his Certified Food Scientist credential from the Institute of Food Technologists.

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