Inflammation is the response of vascular tissues to harmful stimuli like pathogens, damaged cells or irritants. Therefore, an inflammatory response is not only elicited by an infection (external pathogen). The objective of this response is to heal and recover.

During an acute inflammation, several types of cells that are already present undergo activation and subsequent release of inflammatory mediators responsible for the clinical signs of the inflammation. Such mediators cause increased blood flow resulting in redness, increased permeability of the blood vessels resulting in leakage into the tissue (swelling), sensitivity to pain, and chemotaxis in order to attract leukocytes for cleaning up the damage. These inflammatory mediators are quickly degraded in the tissue.

Therefore, the response quickly disappears as soon as the stimulus has been removed. When termination of the inflammatory response fails the inflammation becomes chronic. The types of cells involved change and the site of inflammation undergoes simultaneous destruction and healing of the tissue. Chronic inflammation is associated with auto-immune diseases, allergies and cancer.