Inflammations occur as a reaction to strong mechanical stimuli, extreme temperatures, chemical or biological stimuli and high energetic radiations. The physiological purpose of inflammations is to protect from potentially dangerous stimuli. These stimuli include for instance injuries, foreign particals, heat, cold, UV light, acids, bases, toxins, autoimmunological diseases, bacteria, fungi, viruses, parasites and many more. External signs of an inflammation are an increased permeability of blood vessels which leads to a reddening of the skin, due to increased blood flow. Other effects related to inflammations may be increased temperature of affected parts of the body, impaired functions, pain and swellings. Alongside these local reactions there may be systemic effects, including fever, general malaise, and an increase of protein markers for inflammation.

In case of a local inflammation the blood vessels are dilated leading to an aggregation of blood-cells in the inflamed region. Therefore lymphocytes, macrophages, mast cells and granulocytes may invade the inflamed region. On a molecular level substances like histamine and prostaglandins are released, leading to the mentioned aggregation of blood. Following reactions are changes of the expression of various proteins, many of which are transcription factors. Nuclear factor (NF)-kappaB is a transcription factor that triggers a positive feedback loop. Other important markers of inflammation include interleukins, transforming growth factor (TGF) beta, leukotriens and others.

Inflammations that have no (or no longer) any regenerating effect for the affected tissue are treated with anti-inflammatory agents, like steroids and non-steroid inflammation inhibitors as well as not steroidal inflammation inhibitors.