Inflammatory chemicals, or mediators, such as histamine, bradykinin, prostaglandins, leukotrienes, and cytokines, are substances released throughout the body to signal and facilitate the inflammatory response to injury, and infection. 

Systemic inflammation can also occur, triggered by factors such as chronic stress, infections, or chronic conditions, resulting in elevated levels of inflammatory chemicals throughout the entire body. 

These chemicals cause local effects, such as vasodilation (widening of blood vessels), increased vascular permeability, pain, and the recruitment of white blood cells to the affected area, leading to the classic signs of inflammation: heat, redness, swelling, and pain.