Eicosanoids are signaling molecules made by oxygenation of twenty-carbon essential fatty acids, (EFAs). They exert complex control over many bodily systems, mainly in inflammation or immunity, and as messengers in the central nervous system.
Eicosanoids derive from either omega-3 or omega-6 EFAs. The omega-6 eicosanoids are generally pro-inflammatory; omega-3's are anti-inflammatory. The amounts and balance of these fats in a person's diet will affect the body's eicosanoid-controlled functions, with effects on heart disease, triglycerides, blood pressure, and arthritis. Anti-inflammatory drugs such as aspirin and other NSAIDs act by downregulating eicosanoid synthesis.
There are four families of eicosanoids—the prostaglandins, prostacyclins, the thromboxanes and the leukotrienes. For each, there are two or three separate series, derived either from an omega-3 or omega-6 EFA.