Inflammation is a defense mechanism of the body to protect it from infection and injury.  The inflammatory response is started by white blood cells releasing defense molecules to remove injurious stimuli such as damaged cells, pathogens or irritants. 

A significant part of this inflammatory response is the biosynthesis of eicosanoids by these white blood cells.  Eicosanoids are lipid molecules derived from the polyunsaturated fatty acid, arachidonic acid.  There are several major eicosanoid metabolism pathways in the body, including the cyclooxygenase prostaglandin pathway, the 5-lipoxygenase leukotriene pathways and cytochrome P450 arachidonic acid metabolism pathways. 

Redness, pain, swelling, heat and loss of function in the injured tissue can all result from the inflammatory response.  If the inflammatory reaction becomes uncontrolled, tissue damage can occur.  The inflammation response can be short-lived (acute inflammation) or long-lived (chronic inflammation).  Chronic inflammation can result in amplification of tissue damage and result in chronic diseases such as asthma, chronic obstructive pulmonary disease (COPD), rhinitis, atherosclerosis, psoriasis and arthritis.